Hypnic jerks, also known as sleep starts, can start at any age. They are most common in childhood and adolescence, but they can occur throughout life.
These sudden muscle spasms or twitches are typically harmless and occur as you're falling asleep.
While the exact cause of hypnic jerks is unknown, they are thought to be related to the transition between wakefulness and sleep.
They are generally not a cause for concern, but if they are frequent or disruptive to your sleep, you may want to consult a doctor.
