PC troubleshooting help needed

So, here’s the deal. I put my computer into sleep mode yesterday, and everything seemed totally fine at first. But then, out of nowhere in the middle of the night, the power went out. Now, when I try to boot it back up, macOS won't even load. It just shows that initial startup screen and then immediately restarts itself. Anyone got any ideas what happened?

Just try running a system repair—you can boot the computer using a macOS installation disk or a USB drive and then run the repair tool.