17 weeks and possible contractions?

This is my second pregnancy and I remember with my first my stomach would get rock hard for a second then go soft again. Well last night I woke up because I was uncomfortable and it did this about 5 times over 20 minutes. It went away and hasn’t done it again but has anyone else had something similar to this happen this early? It wasn’t necessarily painful just uncomfortable so I would think that’d mean it’s not too serious?