Hey,
that much difference overnight seems too much to be a driver issue and much less changing something in BIOS.
First I would check if you have a CPU fan failure or starting to fail, like the fan hub being wobbly.
But if you are worried about changes in the BIOS, you can always reset to factory defaults then check option by option.
But maybe its best for you to give us more details about your system.
Good luck
The Englishman