Waking up at 5am every morning

My LO usually wakes up at 3am & 5am for night feed however after 5am feed, he’s always squirming, moving both his hands and legs, unable to get back to sleep until around 6-7am. Any idea why? He’s drinking 90ml two hourly, usually sit him upright for 30minutes after feed, most of the time will burp. #advicepls #firsttimemom