It's not that it doesn't boot, but that the computer simply doesn't turn on. Absolutely nothing happens when I press the power button. Strangely enough, at some point it does turn on. This time it turned on on its own!
I never had stability problems, the computer never did turn off when I was using it. Even now when it does start, it works well.
At first I suspected the power button. But now that its on, I tested. Every time I press the power button, the shutdown dialog appears. So the power button seems to be working well.
The computer is connected with a LAN cable to the motherboard; there are two LEDs. When I switch off the power supply, the LEDs go off, when I switch it on the LEDs start blinking again.
I guess it comes down to the motherboard or the power supply. Which one is more likely to be at fault here? Unfortunately, I don't have any replacement parts to test. I would have to order them. Where should I start?
Btw, I have the habit of disconnecting the computer from power at night via a power strip with a switch. Is that maybe not a good idea?