How can I stop my hand from going numb or shaking when I laugh.?!

I have this thing and I don't know if anyone else has it. But when I laugh my hands go numb and I can hold anything. Same thing happened to me today in school and i couldnt hold my pen or write. Then when the numbness went away I was shaking and couldn't write.
Does anyone know the cause of this and how I can stop it?