I involuntarily slapped my doctor during a strep test
Do you accidentally slap people a lot?
Yes, I've noticed that when I get nervous my hands immediately react.
Wow, slapping the doctor is a kind of extreme reaction. You should probably try figure out a way to stop that as an automatic reaction. You could get in trouble in some settings.
I reacted to the needle in his hand.  Many people would do the same!
Then those people should also try and work on stopping that kind of reaction.  Did you consider mentioning to your doctor that this happens to you a lot?  Maybe he could help you treat it.