Contraction?

I’m 36 weeks and earlier when I was laying in bed I felt this pressure or tightening build up in my uterus and abdomen for like 30 or more seconds and then it lighten up. I tried to move to see if I was just laying weird but I could barely do that and it still didn’t help. I’m a FTM so I don’t really know what contractions feel like or what is the norm so if someone can help me 🤗 thank you!