PC wouldn't come out sleep mode and then wouldn't boot properly

Hey guys, I am hoping you can help me. I put my pc in sleep mode when I go to sleep and I have been doing so without problems. This morning when I woke up, my pc would not wake up. I would hit a key or push the power button and nothing would happen, only the numpad light would go on when I pushed a button and would turn off as soon as I let go. I hit the switch on the back of my pc, waited 10 seconds, then turned my pc back on. There were no problems initially, the Gigabyte splash screen came up but the windows did not shut down properly screen did not show up, just a black screen with a blinking dash.

It was like that for a minute at most then it was just a black screen. I went to another pc to see what was wrong with mine. I came back a few minutes later and saw my mouse cursor but it would not move when I moved the mouse, only the loading circle showed up. I left again and when I came back, the browser page I had on when I went to bed was on screen but everything was frozen. The start menu, Steam, minimize window, nothing would respond to my clicks. I left and came back again and saw the last thing I clicked, Steam, was on screen and my pc was fine. Does anyone know what happened?

It can very well be a one time thing. You can check some hardware if you so wish though:

https://www.sevenforums.com/tutorials/433-disk-check.html
https://www.sevenforums.com/tutorials/105647-ram-test-memtest86.html

Get HWInfo (start with sensors) or similar temperature app for these two:
Use Prime95 and Intel Burn Test for CPU testing.
FurMark and Intel Burn Test for GPU testing.

I don't know whether people here reckon using sleep mode to be a sensible thing or not. I haven't used it since reading a technical article some time ago about how it can fail to close down or open up properly, and perhaps that's reflected in the experience you had. Personally, I switch my computer off at the wall whenever I go to bed at night and leave the house in the day. I hope it turns out to have been a one-off incident for you.

The only way I can see a room fan being relevant is:-

(a) If turning it off results in an increase in the ambient temperature to the point where the computer fans step up a level to compensate and that results in the computer waking up.

Or

(b) If there's something about the stability of either the power installation in general or the fan in particular that results in turning off the fan causing some sort of power surge or other fault that triggers the computer to wake up.

Neither seems very likely.

Temperature testing is included in the Troubleshooting Steps.

Try plugging the fan into another household circuit.

I wasn't hinting on a temperature problem though.
I said keep an eye on temps if you run those 2 set of tests, they tend to burn CPU/GPU