Restart after login or after Clover boot screen

Hey there, people I'm hoping someone could help me out with this.

I have a ThinkPad X220, specs listed here and I've installed High Sierra on it (works great btw) using this guide and I've got iMessage to work and everything.

However recently basically out of nowhere, my system started rebooting after the boot screen or sometimes after I fill out my password.

Imagine this: computer was off > you power it on > the ThinkPad screen pops up (where you can enter the BIOS), boots in to Clover, you select the MacOS install partition > black screen > ThinkPad screen pops up > boots in to Clover > you select the MacOS install partition > a message that the system restarted unexpectedly, etc. > you hit enter > you get to the login screen, where once you login everything appears to be working fine.

Another scenario: Computer boots up > ThinkPad screen > Clover boots up > you select the partition where you've installed MacOS > loads up the login screen > you login > black screen > ThinkPad screen > Clover boots up... and upon next login you're good, you get a notification that there was a sudden, unexpected restart, a popup window asking you whether you want to report the problem or ignore it and that's it after that I haven't noticed any issues

Hope someone here could help or point me in the right direction.

Thanks in advance!