Early morning restlessness

My baby has been super restless at his 3 am to 5 am feeding (time of waking ranges). However he woke at 3 for eating. He’s been basically tossing and turning for 2 hours. We bed share so I don’t understand he should feel comfortable. I have picked him up and let him rest on my belly. He’ll sleep but I won’t. I’m just so tired at this time of night and I don’t understand why he’s so uncomfortable. He doesn’t burp at night.