"Twitches while falling asleep are called hypnagogic myoclonus, myoclonus being any sort of involuntary muscle spasm and hypnagogic referring to sleep. The twitches occur during very light sleep as the conscious brain gradually relinquishes control of the motor functions. Often they're accompanied by a sense of falling, or the feeling that something is flowing through the body, and sometimes people will experience vivid dreams or hallucinations."

Quoted from one of the many websites that document these muscle twitches. Apparently, it is aka "sleep starts" and "Sleep myoclonus" whose cause has yet to be identified. So now i know "House" has been bullshitting with one of his "differential diagnosis". So ma-lu