That feeling of shaking inside your body when nothing is visibly moving is called an internal tremor. It’s more common than most people realize, and while it can be unsettling, it often has a straightforward explanation. Anxiety is the most frequent trigger, but neurological conditions, medications, nutritional deficiencies, and post-viral syndromes can all produce the same sensation.
What Internal Tremors Feel Like
People describe internal tremors in different ways: a vibrating feeling deep in the chest or abdomen, a buzzing sensation in the arms or legs, or a sense that your whole body is quivering even though your hands are perfectly still. The intensity can range from a slight vibration to something that feels almost paralyzing, and the frequency varies from occasional episodes to near-constant awareness. If someone watches your hands or holds your arm during an episode, they won’t see or feel any movement. That disconnect between what you feel and what’s visible is the hallmark of this symptom.
Internal tremors likely originate from the same brain circuits involved in visible tremors, where the areas that control muscle movement send slightly abnormal signals. But instead of producing a movement large enough to see, the signals stay below that threshold while still being strong enough for you to perceive.
Anxiety Is the Most Common Cause
When you feel anxious or stressed, your body activates its fight-or-flight response. Stress hormones like adrenaline flood your system, increasing your heart rate, tightening your muscles, and making your nerves more sensitive. That combination creates the perfect conditions for internal shaking, muscle quivering, restlessness, and a “wired” feeling that won’t settle down.
There’s also a feedback loop at play. When you start paying close attention to your body (which anxiety encourages), nerve signals feel amplified. Tiny muscle micro-movements that you’d normally never notice suddenly become obvious. Normal shifts in adrenaline feel dramatic. This heightened body awareness can make the sensation persist long after the original stress has passed, because the act of monitoring it keeps the nervous system on alert.
If your internal shaking tends to show up during stressful periods, improves when you’re distracted or relaxed, and isn’t accompanied by other neurological symptoms like weakness or coordination problems, anxiety is the most likely explanation.
Neurological Conditions That Cause It
Internal tremors are surprisingly common in several neurological conditions. A study published in Parkinsonism & Related Disorders surveyed patients with Parkinson’s disease, multiple sclerosis, and essential tremor. About 33% of Parkinson’s patients reported internal tremors, 36% of people with MS experienced them, and 55% of those with essential tremor felt them. These are high numbers, yet internal tremors are rarely asked about in routine appointments.
In Parkinson’s disease, the brain gradually loses cells that produce a chemical messenger critical for smooth, controlled movement. That same disruption can generate internal shaking sensations even before visible tremors appear. In multiple sclerosis, the protective coating around nerves becomes damaged, which distorts the signals traveling through them. This can produce buzzing, vibrating, or tingling sensations that feel like something is humming inside your limbs or trunk.
Essential tremor, the most common movement disorder, typically causes visible shaking in the hands during activity. But more than half of people with the condition also feel internal vibrations, suggesting the tremor signal exists on a spectrum from imperceptible to obvious.
Long COVID and Post-Viral Triggers
Internal tremors emerged as a notable symptom during the Long COVID era. A Yale study (the LISTEN Study) surveyed 423 adults with Long COVID and found that 37% reported internal tremors or buzzing vibrations as a symptom. Women were affected more often: 81% of female participants reported the sensation compared to 70% of male participants.
The tremors in Long COVID can be persistent and disruptive, occurring every few hours or on a near-constant basis. Researchers believe the virus may trigger lingering inflammation or immune dysfunction that affects the peripheral nerves, though the exact mechanism is still being worked out. If your internal shaking started after a viral illness, particularly COVID, this connection is worth mentioning to your doctor.
Small Fiber Neuropathy
Small fiber neuropathy is a condition where the smallest nerve fibers in your skin and organs become damaged. These fibers handle pain, temperature, and certain internal sensations, so when they malfunction, you can experience burning, tingling, and vibration-like feelings that don’t correspond to anything visible. It’s an underdiagnosed condition partly because standard nerve tests often come back normal. Diagnosing it typically requires a skin biopsy that measures nerve fiber density, along with specialized sweat-function testing.
Between 13% and 36% of people with small fiber neuropathy eventually develop damage to larger nerve fibers too, which can affect your ability to feel vibrations and touch normally. Causes include diabetes, autoimmune diseases, and sometimes infections, though in many cases no clear cause is found.
Medications and Substances
A long list of medications can trigger tremors, including the internal kind. Common culprits include asthma inhalers (especially albuterol), antidepressants like SSRIs, mood stabilizers such as lithium, stimulants including caffeine and amphetamines, certain seizure medications, and steroids. Too much thyroid medication can do it as well. Alcohol, nicotine, and some antibiotics round out the list.
If you started a new medication around the time the shaking began, or recently changed your dose, that’s a strong clue. Drug-induced tremors typically improve when the medication is adjusted or stopped, though you should never change your dose without guidance from whoever prescribed it.
Magnesium and Electrolyte Imbalances
Magnesium plays a key role in regulating nerve and muscle function. When levels drop too low, calcium flows more freely into nerve cells, which overexcites the muscle nerves. The result can be twitches, tremors, cramps, and that internal shaking feeling. Magnesium deficiency is fairly common, especially in people who eat highly processed diets, take certain medications (like proton pump inhibitors), or have digestive conditions that impair absorption.
Other electrolytes matter too. Low calcium and low potassium can both increase neuromuscular excitability, producing similar sensations. A simple blood panel can check these levels.
How Doctors Evaluate Internal Tremors
Because internal tremors don’t produce visible movement, there’s no single test that captures them directly. Instead, doctors work through a process of elimination. A neurological exam checks your reflexes, coordination, strength, and gait for subtle signs of conditions like Parkinson’s or MS. If there’s reason to suspect nerve or muscle involvement, electromyography (EMG) and nerve conduction studies measure how well your muscles respond to nerve signals and whether the nerves themselves are conducting properly.
Imaging like an MRI of the brain or spinal cord can reveal the nerve damage characteristic of MS or structural issues contributing to tremor. Blood tests screen for thyroid dysfunction, vitamin deficiencies, and electrolyte imbalances. For suspected small fiber neuropathy, a skin biopsy is often the most definitive test.
If all tests come back normal and anxiety or stress is prominent, that itself is diagnostically useful. It doesn’t mean the sensation isn’t real. It means the nervous system is generating the signal through a stress-driven pathway rather than a structural one, and the approach to managing it shifts accordingly toward nervous system regulation, stress management, and sometimes therapy or medication for anxiety.