I just wanted to add this in case someone has this and wants to know more about it.

It's called "partial seizures" where your body convulses, but you don't lose consciousness. It happens a lot of different ways but one way is when all the muscles in your body contract and at the same time rapidly vibrate kind of like shivering.

Some people have it bad where it's reoccurring. For some people like myself it only happens when recalling certain memories that I guess are so traumatizing that you can't handle it.

...
I guess it's rare.