I seen someone else post about this and someone commented saying that it could be the baby literally shaking its leg/arm to get the umbilical cord off of it.

I have felt it to. not all the time just random times. i don't think it's anything to worry about. but hey if you call your doctor and it is something to worry about let me know!!

Crotch lightning

I have felt it before! Not on a regular basis though! Im pretty sure it's normal , I've seen multiple posts about the same thing and no one has ever said anything bad