Braxton Hicks or something else??

Ka

I’m 19 weeks 2 days pregnant and for the last week or so I have noticed some tightening in the uterus. It comes and goes randomly and doesn’t hurt at all and it’s not gas. It feels like my uterus clenches for 10 seconds or so then relaxes and it may be hours before it happens again, like it said it doesn’t hurt. What is this? Is it something I should be worried about?

FYI it’s my first pregnancy and haven’t felt baby move yet.