Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Myoclonus ?
    ### Response:
    Myoclonus refers to a sudden, involuntary jerking of a muscle or group of muscles. In its simplest form, myoclonus consists of a muscle twitch followed by relaxation. A hiccup is an example of this type of myoclonus. Other familiar examples of myoclonus are the jerks or "sleep starts" that some people experience while drifting off to sleep.
    