After crashing my PC has became very unresponsive and slow.

Apr 25, 2019
I was playing Sekiro on steam (I have a mod installed but it's only to show PS4 controller buttons instead of Xbox) and my game crashes during a loading screen. I should say my entire PC crashes rather. I let it set for a min after the game crashes and it just goes to a black screen and is totally unresponsive, after a few minutes I hit the restart button and it instantly starts lagging. Out of the 3 applications I have on start up it take around 10 minutes for them to actually load. I'm new to computer building and I followed alot of information online on how to set up my drivers and make sure everything is compatible considering I just built the thing and it's been running fine for the last 1-2 weeks. I'm just wondering how to troubleshoot the problem and get her back to her good ol self.
I think you'd get a better response if you posted on the hardware threads rather than here. Keep in mind for future reference. A few things to start with.

Specs of system?
Is Windows (I assume) configured for crash dumps?
What is hardware performance like during gaming?
Temperatures of CPU and graphics card?