My whole body locks up when I workout

So I have this think where when I’m working out or I move my hands to quick they lock up and I can’t move them for like 10-15 seconds. it happens to my legs and makes me pretty much just become a log and fall or something, my hands, fingers and feet. They just freeze in the position there in. It happened pre-pregnancy but not as much as it does now that I’m 27 weeks pregnant. I’ve told my doctor and she doesn’t really know what to think about it. I’ve gained a little extra weight than I was supposed to so far but she said most women she sees gain the amount I have (30 pounds at 27 weeks). Could it be due to weight? I’m really at a loss for what’s going on.

I also have RLS but I know that’s pretty common and don’t think the two would be related?