I've had that before, it's weird when I'm sitting there abd class and I get a twitch. Most twitching can be seen in people who are in a growth spert. Ussaly people grow out of it. My brother is just getting to this point and it's funny when he twichs. It's normal, I would have full body twiches too. If it makes you feel better mention it to your doctor next appointment. :)
I think it means you should go see your doctor ASAP...Have you discussed with your parent(s)? May be nothing, but well worthy being checked out as soon as possible
JIm