Is it normal to be able to vibrate my right hand at will?

Brushing my teeth, masturbating (male), and clicking really fast, are the main ways I use this. I can also do it with my head. I would assume I'm just channeling my high muscle tone and tremors (my hands shake slightly just all the time), or restlessness. I don't know how to describe exactly how I do it (what muscles I use), but a muscle an inch-wide bulges up along the side of my arm in a way I can't make happen doing anything else.