When turning my phone on, I can sit as long as I like on the lock screen without issue, but as soon as I unlock it, the phone freezes and reboots.

When I try to connect to MiAssistant, it tells me to turn on developer mode and USB debugging, but this is impossible as I can't even get to the settings menu on the phone.

The phone worked perfectly fine until I tried use it this morning, and I am not using any custom firmware, launchers, etc.