"JG" <no-spam@please.com> wrote in message
news:mn.ca9d7d7237e05164.33676@please.com...
SNIP
> When I plugged my USB Stick, I accidentally touched the case with the
> metallic end of the key. As I did this, the computer rebooted instantly.
>
> Later, I removed the case cover to check if there was room for another
> disk drive. Upon closing the cover, the computer rebooted as soon as the
> cover touched the case.
>
> While the humidity was a little low, I did not feel a static discharge at
> all.
>
> As additional info, the computer is plugged in a ups with the required
> grounded wire.

Years ago I traced a winter time pc rebooting problem to a cheap pc power
supply. That power supply used a grounded cord, but inside the box I found
the manufacturer failed to connect the ground wire to anything (unbelievably
bad, but true).

I strongly suspect you have found a grounding problem. Bad grounding could
result from a bad power cord, bad power supply, faulty UPS, faulty wall
outlet, and more. Ask a friend with a Multimeter (Volt/Ohm meter) to test
the electrical ground path of the computer case and the system board to the
AC outlet ground lug. Tighten loose motherboard screws too (often at least
one will be metal, screwing into a metal stud on the case).