Not normal rapid movement?

I'm 24 weeks and the past couple of days I've been experiencing very strange rapid movement that has me a bit worried. It's not like a kick or flutters it literally feels like he's seizing. I looked it up and others say its hiccups but I feel like that would be a constant rhythm. This is literally about 5 seconds of just extreme rapid movement. I'm going to call my OB on Monday but I wanted to see if others are experiencing this. I can't sleep at night because this is when it usually happens and it worries me.