Why does my baby do this in his sleep?

ryn

When I lay him down to sleep he will be fine, then on and off will grunt like CRAZY and make these whining grunting sounds and kicks his legs / arms around / wiggling around. He does this every single night aside of being awake every hour. I’m exhausted. During the day when he’s sleeping he doesn’t do this ( he has his days and nights mixed up as well ) I don’t understand why he does this and especially only at night?