Alright, so, last night, around 04:30 again, the computer came back on, this time i managed to do powercfg -lastwake, and i got this:
Wake History Count - 1
Wake History [0]
Wake Source Count - 1
Wake Source [0]
Type: Wake Timer
Owner: [PROCESS] \Device\HarddiskVolume2\Windows\System32\services.exe
Owner Supplied Reason: Windows will execute '\Microsoft\Windows\Media Center
\mcupdate_scheduled' scheduled task that requested waking the computer.
By the looks of things windows media center is looking for an update at 04:30...