My LO went through a phase of this, though it could be 330.4am.5am etc.
as pp said of naps - maybe not enough or too much sleep in day? What's lo routine?
Maybe overtiredness.
Hungry-I upped her intake and gave an couple extra top up feeds. Especially before a nap.
Cold? I put heating on 3am till 6am at low heat just to take chill off.
Could try the trick of waking lo before the usual time. Just enough to disturb them. Some say stroking cheek, some say knocking cot slightly, and resettle them quick. What ever you prefer. Personally my LO woke up earlier as a result of me doing it.
Developmental? Big changes at 6 months
What time lo going bed?
Is room dark enough?
Personally nothing I did worked, and I will just leave her if she wakes now (we got 530am wake up at the moment approx) I leave her babbling etc until she shouts for her dummy. Or needs some comfort as if I went to her to soon she thought it was get up time 😂 then she drift off about 615/630am till I get her up at 7am.
If your happy cosleeping then carry on. Personally no matter what I will not cosleep but that's my personal preference