When I was on narcotics for pain I had myoclonus. Sudden noises or surprises would make my entire body jump, one giant jackknifing twitch. But on a lesser scale, it was evident brief movements of large muscles groups where there'd be a big "contract" and then a slower "relax". Like, my ankle might suddenly twitch up, then gradually go down. Then an arm, a finger, my head. They fit the description myoclonus, which is associated with opioid painkillers.

Are you one pain meds?