Strange hand spasms/shakes?

so every once in a while, i get these weird muscular spasms/shakes in my right hand. recently i had a really bad one, where my hand was shaking terribly, and i had to use my left hand to hold it steady so i wouldn't drop what i was holding. i do have petit mal epilepsy, but my neurologist said it isnt associated with my epilepsy, so i have no idea what's wrong with it. but it really freaks me out and it's just uncontrollable whenever it happens. any idea what could be causing it? i'm young, so i doubt it would be arthritis or anything..its just so weird. :(