I use my desktop as a backup alarm clock. I set the time, turn the speakers to a reasonable volume, and turn off my monitors. Is there any reason that somebody can thin of why it's turned off overnight the past 3 nights in a row? 3 nights ago it was a scheduled Windows Update that let me get up late. What's been going on the past two days?
I'm mostly posting this just to whine.
There is a setting in the Power Saving/Energy Management options where it turns off after a specific idle time. But usually that's not a shutdown, just standby and/or hibernate.
Alternatively just let Folding@home run at night 
I plan on getting Folding@home setup so I can run it in off hours. And all my power saver stuff is set to never shut down, hibernate, sleep, whatever, under any circumstance ever.
If it isn't power savings, then could it be a power source issue? I have my HTPC set to turn on when power resumes (as well as my TV) so I can turn on my power strip and everything runs. If you are relying on your PC to wake you up then setting this in BIOS would make certain the machine comes back on in case of a power blip/failure.
Not that this definitely your issue, but it would still be a good idea to make certain that motherboard setting is adjusted properly. I don't know much about Windows or if an update would change your power savings settings, but you may want to double check that those settings are correct.
check windows update options, if it says "automatically install updates" you can be sure that the machine will restart on its own.
Are you sure it's shutting off or is it maybe going into deep sleep mode?
Well, I think it's actually restarting. I wake up and it's on but none of my previous windows or the programs I start up when I boot are running.
Yeah, but three nights in a row? Seems a bit odd to me.
Check your event viewer and see if your computer is crashing causing it to reboot.
Updater starts update, fails to apply update, rolls back, schedules a new update for the next night. Might want to check update settings and clear update cache which if I recall correctly is in "%windir%\SoftwareDistribution\Download".
That is a really energy inefficient alarm clock. You can use your phone for the same thing, and you most likely leave that on at all times. Why use the computer?
I'd thought of that, but wouldn't that trigger the "Update and Restart" option in the start menu in the evening before this occurs?
Backup clock set for 20-ish minutes after my primary alarm. I use my phone as well, but on days where I'm studying late and can only squeeze 3 or 4 hours sleep in it helps to have an alarm that I have to get up and out of bed to disable. I agree, but it's the University's dime for power. Part of why I want to set up Folding@home to take advantage of the situation.
Yes, it indeed should trigger a update if you restart or shutdown with the caveat that at least the Windows 8 I currently use on one machine that has updates pending will only inform you on login that you have updates pending, but won't say the same thing when you bring up the shutdown menu. My main point was to systematically exclude things by testing them, to find the root cause.
Trust me, if you're tired enough, it won't matter if you have to get up.
Ah, so as long as you're not paying, you don't care if you waste electricity. Charming.
Thanks for the life advice. Really appreciate it. I'll remember this moment forever. Your commentary is great. I especially liked the part where you assumed something about me based on behavior of mine. Also the part where you told me about how my sleep schedule works? Who the fuck made you the expert on my life?
There's a difference between not caring about power usage and placing something far from the top on my list of concerns seeing as I'm constantly working when I'm at school. We're all shitty people if we go through and analyze every waste and excess in our lives. How about we worry about ourselves and not point the finger, eh? When I'm not at school, my home is fully powered by solar panels. I've developed certain power usage habits as a consequence of this, seeing as I have unlimited low-impact electricity at home. So sue me.