Body spasms/jerks

Does anyone else experience body spasms during a session? Like where your body kinda jerks or twitches because of how strong a sensation is?

It happens to me specifically when I rub my frenulum with my left middle finger while flicking my left nipple. I have no idea but it drives me wild. I can feel my dick stiffen and my balls get tighter in the sac, and then every 5 seconds it’s like the sensation is so powerful my upper body just jerks. It’s practically euphoric.