Could be hungry assuming that you feed him or at least try could also be gas.... For my kids I massage their tummy and move their legs towards their tummy usually helps as long they have gas drops you can buy
I tried feeding him and he wouldn’t take it I even tried a bottle because I breastfeed so I pumped and tried that wouldn’t take it I rubbed his tummy and did Bicycle legs he just wasn’t having it Lol so after 30 mins of crying and me trying to figure out the problem he fell asleep but I think he is teething because lately all he wants to do is suck on his fist and he’s been drooling more than he usually does so I was thinking maybe it’s that