I have a brand new windows 8 computer and I will shut it down properly and then a few minutes later it will power itself back on and go in and out of sleep mode. I had the same (new) computer before this one and it did the same thing but exchanged it because I had issues with 8.1. I thought it was just that computer but now I am having the same problems. Any suggestions?
Somewhere inside your bios, there's a setting that tells the motherboard to either let the BIOS or the O/S control the power settings. I forget which one to pick. However, whichever it is set to now, set it to the other.
I had this problem on my father's MSI P67A GD65 motherboard and fixed it with that setting. It would not go to sleep, but I changed it to resolve the issue.
unplug the network cable and see if the machine stays asleep.
Sometimes network drivers have Wake on lan (WOL) set and another computer attempts to connect to the network card and wakes the machine back up. (other computer on same homegroup, or a media extender, xbox,...)
-to fix you need to config the network driver and not allow it to wake the computer.
also, to confirm:
start cmd.exe as a admin (windows key +x, then type a)
powercfg.exe /lastwake <- this will display what the computer thinks woke it up
Also, note: your computer might be attempting to go to sleep, start to shutdown. The OS will tell all the programs to shutdown
but a program has the option to block the sleep attempt and the system will come back to life (never did actually go to sleep)
common with media players that can stream or provide service to other computers or devices on the same network. You have to configure the
power management to not let them block the sleep request.