Hypnogogic jerks are also known as sleep starts or hypnic jerks. They're strong, sudden, and brief contractions of the body that occur just as you're falling asleep. ... Hypnogogic jerks are also sometimes called sleep twitches, night starts, or myoclonic jerks. A myoclonus is an involuntary muscle twitch.

Why Do People Twitch in Their Sleep?

Also known as sleep starts or night twitches, these movements are generally harmless, though your partner might not appreciate the occasional kick. ..."During the phase of falling asleep, we often have a quick dream - or dreamlet - which, for many people, is about falling," says Bils.

Myoclonic twitches or jerks usually are caused by sudden muscle contractions, called positive myoclonus, or by muscle relaxation, called negative myoclonus. ... Other familiar examples of myoclonus are the jerks or "sleep starts" that some people experience while drifting off to sleep.