Hypnic jerks, also known as sleep starts, are sudden, involuntary muscle contractions that jolt you awake just as you’re falling asleep. “Up to 70% of people report having this strange jolt,” making it a common but startling experience.

One theory suggests that as the body relaxes into sleep, the brain may misinterpret this as falling and sends a burst of neural activity to “catch” the body, triggering the jerk. Another explanation is that the nervous system struggles to transition smoothly from wakefulness to sleep, causing brief misfires.

Stress, anxiety, and fatigue can increase the likelihood of these jerks. When the body is overtired or on high alert, the nervous system becomes more prone to these sudden movements.

Although harmless, hypnic jerks can be frustrating, especially if they disrupt sleep. Understanding that they are a normal part of the sleep process may help reduce any associated anxiety.