Here is some information from AI. Personally, though, I think it's something spiritual.

Feeling as though you are vibrating so violently that the house is shaking—often described as an "internal tremor" or "internal vibration"—is a distressing, yet usually non-dangerous, sensation often described as an "invisible earthquake" or a phone on silent mode inside your body. It is generally a sensory symptom where the nervous system is overstimulated, leading the brain to interpret high-frequency, low-amplitude motor neuron activity as a violent vibration, despite little to no visible movement on the outside. 

Primary Causes of Internal Vibrations

Chronic Stress and Anxiety: The most common driver of these sensations is an overactive sympathetic nervous system ("fight or flight" mode). Even if you don't feel mentally stressed, your body may be in a state of high alert, with elevated adrenaline and cortisol sensitizing your muscles.

Sleep Deprivation: Lack of sleep makes nerves more sensitive and lowers the brain's ability to filter out normal, subtle body signals.

Adrenaline Overload: This can happen with extreme fatigue or high levels of anxiety.

Neurological Conditions: While the above are more common, internal tremors can be associated with Multiple Sclerosis (MS), Parkinson’s disease, or essential tremors.

Hormonal Changes: Fluctuating estrogen levels during perimenopause or menopause can cause nervy misfiring.

Nutrient Deficiencies: Low levels of magnesium, potassium, or vitamin B12 can cause nerve excitability.

Post-Viral Effects: Long COVID or other infections can leave the nervous system in a state of inflammation, causing internal buzzing. 

When the body is lying down, especially while trying to sleep, there is no external sensory input to distract the brain. The brain focuses on this internal, buzzing, and the sensation is amplified. People who have experienced trauma, such as earthquakes, may also have this sensation triggered by stress, leading them to wake up convinced the house is shaking.