Hypnic jerk
INVOLUNTARY TWITCHES
Sleep start; Hypnagogic jerk; Hypnogogic jerk; Hyngaogic jerk; Nap jerk; Hypnic Jerk; Night start; Night starts; Nod-and-jerk; Nod and jerk; Hypnagogic myoclonic twitch; Motor start; Sleep jerk; Sleep-start; Hypnic myoclonia; Sleep myoclonus
A hypnic jerk, hypnagogic jerk, sleep start, sleep twitch, myoclonic jerk, or night start is a brief and sudden involuntary contraction of the muscles of the body which occurs when a person is beginning to fall asleep, often causing the person to jump and awaken suddenly for a moment. Hypnic jerks are one form of involuntary muscle twitches called myoclonus.