Firstly, I want to say that, first I thought this was a graphics card issue, although i'm not completely sure, so please move this to the appropriate section if i'm wrong.
Recently, my computer has been experiencing huge lag spikes during games, followed by a scrambled boxy version of what was on my screen. It's quite difficult to describe at the bottom of there question are some pictures of what my screen looked like when the issue happened.
The screen was static and I couldnt do anything, both the keyboard and mouse didn't do anything, however as well as this, when I went to shut down my computer via the button, rather than having to hold it down in order to force it, I would only press it for half a second and it would instantly shut down. This would happen initially during games, becoming more frequent, but when i went to do a virus scan in safe mode, the same thing happened before the scan could finish. It happened a few days ago, then stopped for a bit, but it started again recently. I think this is a graphics card issue, but i'm not completely sure, so any help with finding what this is exactly would be great.