So, this has been happening for a long time now. Whenever I go to turn my computer on while it's upright, it boots up and stays on for about a minute. The screen then goes black, the fans on gpu stop running, but all the case fans run. I have an xfx rx580 8gb gpu (this is a replacement after the original one started experiencing this problem. This is one of the reasons why I believe it isn't the gpu) I'm not entirely sure what it could be, as I'm not the best at diagnosing PC issues. (BTW, I used a vertical gpu mount just to see if that would work, but it still reciprocated the same problem) I'm getting sick of wasting a bunch of desk space for this computer, plus I can't even see the pretty LED lights in it because it's sideways 😔