[SOLVED] Intermittent black screen on reboot

[blacktrance]

4790k, ASUS Z97 Pro, GTX 1070

I shut down and unplug my computer every evening, and in the morning it normally boots fine. But if I need to restart, it often just displays a black screen, without showing the ASUS logo first. When it's in this state, restarting it, shutting it off, or even unplugging and replugging it doesn't help - but sometimes it randomly starts booting properly again. Oddly, if I press the power button that's directly on the motherboard, it always boots succesfully.

The motherboard shows code A0, which apparently means that the POST is successful. I'd suspect the graphics card or the monitor, but both work just fine when it boots normally.

This problem started fairly recently and I haven't touched the BIOS in a long time.

 

[blacktrance]

Update: It seems to be booting but the graphics card doesn't turn on, because something probably related also happens when I'm in Windows. It doesn't seem to be related to being under load - it's equally likely to happen whether I'm gaming or browsing the Internet with a few tabs. Any music keeps playing, the system seems to respond to alt-tab (if I'm in a game and alt-tab out of it, the game audio stops), but my monitor continues to display the same last frame.

Since this happens when it's supposed to show the Asus logo, it can't be a Windows driver issue. Not an overheating issue either, because it sometimes fails to turn on even after the computer has been shut down for hours.

 

[blacktrance]

tl;dr: Replacing the CMOS battery seems to have fixed it.

Among the other issues my computer was having, on boot it displayed the time it was shut down instead of the current time, and Windows time would continuously fall behind despite me syncing it. I looked up that symptom and read that it could be the result of a dead CMOS battery, so I replaced it. It's been a week and the other issues seem to have stopped too. I guess the battery died because I unplug my computer every evening, but I'm surprised it would cause these kinds of issues.