Why does he do this when he eats?

sometimes when my 3 month old gets hungry i will start to feed him and while he is eating, he gets wiggly and wont sit still. he grunts and gets a lil fussy. I will take the bottle away to see if hes not hungry but he starts fussin' and i give it back to him and he starts eatin and does it again.Sometimes we repeat this 3 or more times before he takes his formula and stops wigglin. Hes not sick or anything i that has anything to do with it. is it normal? im thinkin he mite has gas but he does this A LOT