Might be hiccups. My daughter had them all the time. Quite fun :) lol
I had it happen during my pregnancy. I honestly thought the baby was having seizures inside me. I even had them do an ultrasound to look at her brain. Conclusion was that it is normal and its muscle spasms because their nervous systems aren't fully developed yet.
My DD and DS did it totally normal just baby having an excited wiggle :)
I see this question a lot and the consensus is that it is normal. My son did this too and I think it is them just testing out their reflexes and almost "jumping" in there. If you are concerned then speak with your doctor for sure.
My now 3 year old use to do that when I was pregnant with her. I asked my doctor about it several times when pregnant with her and he said some just do that reflex and I shouldn't worry. I know everything turned out perfectly fine with her. Shes always been heathly and happy. I'd try not to worry, but I would still mention it to your doctor. I don't have an exact answer, but I hope this can at least ease some anxiety for you.