Not sure if this is normal or not?

For a while now (I can’t be sure exactly when they started, but it was at least five years ago), when I get tired/haven’t been getting the proper amount of sleep, I have these weird body shakes. They’re pretty violent, or at least they feel that way. My back and shoulders get painfully tense and the rest of my body just convulses. It comes and goes in waves. I’ll convulse for half a minute or so and then be fine for a moment or two until it comes back.

I guess I thought, at first, when I started really thinking about it, they were caused by me being cold, but the shakes aren’t like regular ‘I’m cold’ shivering. I can never really be sure if the temperature has anything to do with it, since I am almost always cold. They seem to happen most when I have been short of sleep and I am still staying up like an idiot. Like right now.

I’m just really not sure what to think of them and I want them to go away. I don’t even know if this is an unusual thing that I should be worried about.