After restarting/rebooting, does it still boot to BIOS?
Usually that´s a safety feature, if the computer thinks something is odd with BIOS settings and doesn´t run stable
Eventually the boot order is not set correctly anymore.
ASRock H310CM-DVSThe motherboard thinks something is wrong and tries to help, really normal for this. I don´t think you can or should disable this feature.
Which motherboard are you using?
The feature is named Boot Failure Guard Message
"If the computer fails to boot for a number of times the system automatically restores the default settings. "
I think this will happen as well, if the PC shuts down a couple of times as well.
A UPS would be the best option, Sometimes an outage can corrupt the file integrity of your storage and might lose data or the system can´t boot anymore.