Okay, this is a first. When I booted up my computer, I noticed the idle temps rising to much higher degrees than ever before, even when the CPU load was at 0. Through my incredible detective skills I deduced something may be off inside the case, so I looked through the window on the said case only to notice the CPU fan not spinning at all.

After I shat some bricks and survived a mild heart attack I turned off the computer, opened the case and fiddled with the fan. There was no resistance when I flicked the fan with my finger, it span normally. I then blew some canned air into that thing just to make sure there wasn't any dust and then turned on the computer. To my amazement, the fan now started to spin normally, but I still wonder why it had stopped the first place.

All the connectors were in place, there was not that much dust piled in the fan nor was there anything blocking it's movement. I really don't know what happened.

But as it did happen, I don't trust that thing anymore. Does any of you have any idea why the said fan decided to rebel? Should I replace it?

could be a few knacked ball bearings
or the grease drying out
best to replace it to be sure

If the fan has had a lot of working hours it may be time to replace it, if you still have the problem with a new fan in place you may need to fix/replace the PSU. But I would start with the fan as it's the least expensive part.

By the way you can use something like HWMonitor to check on temps, fan RPM's and voltages.

I shall give it a go :D

It might have had a bit too much to drink at its office party last night and had trouble waking up.
When the CPU, GPU and PS fans get into a drinking contest, the result aren't pretty.

i tend to think that the psu fan always wins
its much bigger the other fans just cant compete

But yes, could it be the PSU? All the other fans worked like they should and the CPU started to work after the restart. I just don't know, this has never happened to me before and this computer isn't that old, it was assembled in april this year...

Serious answer - it was probably a loose connection you cleaned up when you investigated. Stop worrying, long as it's spinning now.

A PC PSU supplies different voltages to different parts of the computer, if one voltage output were to fail completely then your computer would not start. I personally think your CPU fan was just stuck. Keep an eye on it but it's likely to be a one time event.

I wouldn't trust that fan, not after that. It's not worth the risk. CPUs are expensive, fans are cheap.

If you can replace the fan - maybe keep the heatsink- , do it and keep an eye on that fan until the replacement arrives.

Maybe you can reuse it as a case fan or something, but I wouldn't jeopardize the CPU.

https://www.youtube.com/watch?v=O8v09-wlFiM