Have you ever been lying there, or lying next to someone, and there was a sudden jerk or twitch? And they seem to happen all through the night without anyone waking up or experiencing some sort of crazy dream?
These are called hypnic jerks, or sleep starts. They are involuntary muscle contractions that you may experience during the night, sort of like a muscle twitch. Hypnic jerks are referred to as a type of myoclonus, and is the equivalent of a hiccup, or rapid, involuntary muscle movements. Hypnic is short for hypnagogic, which means the transition from wakefulness to sleep which is when these twitches occur.