Why do people shake before falling asleep?

People may shake or experience muscle twitching before falling asleep due to a phenomenon called hypnic jerks or sleep starts. These involuntary muscle contractions can occur as the body transitions from wakefulness to sleep, often triggered by the relaxation of muscles and changes in brain activity. Additionally, anxiety or stress can contribute to this sensation. While usually harmless, frequent or severe occurrences may warrant a discussion with a healthcare professional.