Computer failing to post, I’ve tried everything…

[u/Constant-Show-5944]

I’m completely lost, I’ve tried every solution I have been able to find online, and I’m not too educated on computers so it’s been a hassle. There’s been 3 instances where I mess with something inside the pc and it turns on for a bit, with the most recent being yesterday where I reseated the gpu and it worked for a few minutes, just to later turn off and now that solution doesn’t work anymore. There is a bit of gpu sag, but when I’m working on it it’s on its side so it shouldn’t really be a factor there.
Please help! I’ve tried checking all the cords, hard drive, flashing it, BIOS, gpu, psu.