I have more details regarding My computer boots up during the night. I got a used halogen lamp with a transformer and can reliably reproduce the following:
- Computer and lamp are running
- I shut down Windows until the computer is "off".
- I switch off the lamp.
- The computer starts its boot cycle.
- I press power switch to shut down computer.
- The computer stays off until I hit the power button again. (until I boot into Windows 10 and make a normal Windows "shutdown", that is!).
I am not really sure what the reason is and what to do about it. Any ideas?
EDIT: To answer the questions from your comments and "answers":
Sounds like there are elect[r]ical problems within your walls causing power to not run as reliably as it should.
The basic problem (the computer starting unexpectedly) has survived the change from one apartment in one village to another apartment in another village, somewhere between four kilometers and three miles apart. The "new" (used) lamp I got for my new desk in my new apartment just made the issue reproducible.
Are they both plugged into the the same power circuit
Yes, they are plugged into the same power strip. I have tested a surge-protector and a normal strip, and I have tried to put them on the same power circuit but different outlets. When I plug the lamp into a different power circuit, the problem is no longer reproducible. Other unknown devices on the same circuit still trigger my computer's bootcycle from time to time.
[After using the power button] It stays off even if you the switch the lap on and off again?
Yes, it does. Only when I shut down Windows, it can be booted somehow from the outside.
Desktop or laptop computer?
Desktop computer. Self-assembled. It did work correctly for at least one year with Windows 7.
Do you have BIOS settings for advanced power management? Like "Restore from AC power loss"?
Yes, and it is already set to OFF.
Sounds like it might be an issue with the power supply then.
I have switched to my spare PSU, the problem remains.
is that light a two prong or three prong plug?
It's a two-prong plug.
A surge protector power strip can bypass superior protection inside the PSU (explains why a spike is seen by a computer's power controller).
I have tested that the behaviour is the same with a normal power strip.
Is the power strip connected to a two prong or three prong receptacle?
A three-prong receptacle.
If three prong, does a dedicated ground wire properly connect back to the breaker box or did some previous person have contempt for human safety?
The wiring in my current apartment should have been made in the mid-90s according to the then valid German VDE. In the previous apartment I had the same problem, the fixtures were originally from the 40's, but should have been completely replaced in the 2000s by a VDE-bound electrician.
Is polarity correct?
Not sure what you mean. Both PSU and power strip shouldn't distinguish between phase and ground.
Is motherboard connected to a baseplate via many conductive standoffs or just one?
About six to nine brass-colored metal standoffs.
An EMF spike that can affect @Alexander's display like that
My "display", a Samsung TV, is not affected by a brown-out. I can switch to TV mode and it runs through without being affected by the lamp, although the lamp is placed exactly between display and computer, with more or less equal distance to both, and the display also is on the same power strip.
does your computer have a remote control to turn it on/off?
The TV has a remote control, but the computer doesn't. The TV would then have to wake the PC via HDMI, but I have not found such a button on the remote. I don't have a blutooth dongle, NFC or WiFi device that I know of. I have disconnected Ethernet but the problem remains.