Not too sure really. Probably just a phase, how long has it been going on? What time does he go to bed?
I think if it was me I would persist with the resettling (though I am not as sleep deprived and exhausted as you are probably feeling). Could one of you lay on the floor next to his cot and 'pretend' to rest and hope that he follows suit. I still do this occasionally with Mr.2 in our house when he is unsettled. He thought it was funny at first but now he will rest and when he sees my eyes are closed and that playing isn't on the agenda he gives up and goes to sleep.
No way that you can start your day at 4am
You could try dropping a day sleep I guess but he seems pretty young for that.
I am sure that one of boys has probably done this in the past but it must have been shortlived as I can't remember it!
ETA : he isn't cold or something like that is he?
Edited by Caro07