well I know that I have to be in BIOS, but what excatly am I looking for???
There are no bios settings that pertains to the power supply; there are simply no adjustments to it that can be done through software. In fact, there's not even a data link between the two, all there is is the "power good" signal that goes active once voltages have stabilized when you throw the power switch, and tells the computer hardware it's safe to switch on...
When you boot up your system next time, check that everything looks alright in the BIOS setup, ie any changes you may have made in the past are still correct, and that the date and time display is accurate.
If any of these settings have reset themselves, your mobo battery is faulty or drained (though it usually takes 10+ years for a lithium cell to go flat). If everything has cleared itself it means either some weird fluke happened that reset your BIOS parameters to default, or your computer asks you to enter setup when you boot because all settings have been reset to default due to the battery not retaining them.
Enter any changes you may want once more (including date and time), save your changes and exit. Reset the PC and see what happens. If it asks you once again to enter setup and you find everything is reset, get a new battery, see if that fixes it.
Other than that, no idea what the problem might be.