Amazing i was thinking of posting about a simalar thing that happened to me! It was earlier this week.
I had just woke up from a very real dream and had just started to think about it like you do when you've just woke up after a dream. I was lying on my side when out of nowhere this i felt this huge bolt of what felt like you have described it enter my body at the base of my spine.
It pulled at my lower body and i felt as if i was being pulled away from the bed. It must have lasted no more then 10 seconds but i did feel long at the time. I was unable to move while all this was going on. After it had gone i could move my whole body but when i tried to sleep on my normal side i was always having to turn over or lie on my back as i couldn't sleep with a pain in my back.
Very weird.