What Is The Cause Of Hypnic Jerks?

I have been doing research and i believe im experiencing hypnic jerks. I have them multiple times through the night and some are enough to wake me but other times it causes my wife to make me move away so it doesnt hit her. i hve had them since i was little but never had someone to sleep with that would be able to monitor them. I never knew i had them more then when i just closed my eyes. are these serious or does it happen to alot of people?