Is it normal that when i have sex, i start shivering violently and....

It happened the first time I had sex. We were fooling around when all of a sudden, I felt very cold. The air was not cold, in fact it was slightly warm. I didn't say anything but kept going, thinking it would go away. That's when my teeth started chattering and inside of my legs, arms, torso, nearly everything starting shaking and twitching! It was so violent that my body was actually beginning to shake. Luckily, we were already too into it so I was able to hide it. I suppose he didn't notice or just thought I was so turned on I was shaking *lol*. Afterwards, to keep him from knowing what was going on, I rolled to the other side of the bed and got under the covers, trying to stop shaking, get warm, and keep my chattering teeth from making noise. But I coudn't stop it, it was like my jaw muscles were making it happen by themselves! Finally, after about thirty minutes, I quit shaking and felt fine, except for still a little weak.

After that, it didn't happen for awhile.

It has happened off and on throughout my life and I've managed to hide it so far from all of my partners. It only happens when I have sex *sometimes* and I'm not nervous or scared when it happens. I'll feel perfectly fine when all of a sudden this takes over. Please help...what is this? Trauma related somehow, like a supressed memory maybe? Or health?

Is this normal??