A great Reddit thread asks "What's something you're pretty sure only your body does, but have been too embarrassed to ask," and comes up with some genuinely great responses.
Sometimes when my mouth is slightly ajar and I turn my head to the left I get a sudden nerve pain and it feels like somebody just stabbed me with a chopstick (Realinternetpoints)
My right arm hurts really bad for about ten seconds every time I sneeze. (The Jigmeister)
I'm late to this… but sometimes I get really sick to my stomach for 10-15 seconds… then I sneeze and feel completely fine again. (_deanna_)
(Image: Freak show 1941, Library of Congress/Wikimedia Commons, Public Domain)