Braxton hicks

So I’m just curious what do braxton hicks contractions feel like? This is my third pregnancy and I’m 30w3d and I’ve never experienced them in my two previous pregnancies. From what I’ve read they say they kind of feel like mild period cramps but I have also been fortunate enough to never have experienced period cramps either. Randomly my stomach will get super hard and it only last about 20-40 seconds then it goes away. I first thought that it was just my baby rolling up in a ball and pushing outwards but maybe they really are Braxton hicks. Has anyone else felt something like this?