Odd hyperactive behaviour?

I'm just asking this because I'm curious, but for some reason sometimes when I'm on my own i have the urge to almost spasm vigorously for a few seconds,and also when I get angry it happens, and when ever rarely gotten into a scrap in my life, my friends have told me i pull a weird sort of face by bearing my teeth and sort of almost spasm, im just wondering what it could be caused by.I'm 15 and a well behaved kid so i think it's strange when i do it.