When my boyfriend and I first started having sex, I used to get the worst cramps in my hands and feet for no apparent reason. It was particularly bad when I was just about to orgasm. I'd also sometimes get the tingly feeling. I never figured out what caused it.

I never experienced difficulty speaking or any kind of shaking like that though. That sounds concerning to me, especially if it has never happened before. I agree with the other comments here - If it's possible, he should go talk to a doctor about it. Even if it ends up being nothing to worry about, I think it's better to play it safe when it comes to health.