I have heard that power buttons have got stuck before....the switch and spring inside the button is faulty or going bad and can and should be replaced.
Seeing that the case is fairly new and mordern, if it is still under warranty, I would consider having it replaced.
Now, your BIOS should be fine since it repaired itself and I wouldn't worry about it. If you want to you could see if there is a BIOS update and install that. But be very careful when doing so. If not done correctly you can brick your system (fry it) rendering it useless.