What's the noun for twitchiness? Here's the word you're looking for.
twitch
A brief, small (sometimes involuntary) movement out of place and then back again; a spasm.
(informal) Action of spotting or seeking out a bird, especially a rare one.
(farriery) A stick with a hole in one end through which passes a loop, which can be drawn tightly over the upper lip or an ear of a horse and twisted to keep the animal quiet during minor surgery.
(physiology) A brief, contractile response of a skeletal muscle elicited by a single maximal volley of impulses in the neurons supplying it.