I just built a new computer at the beginning of this month. I think this problem has been occurring since I first put it together.
It restarts itself seemingly randomly when I walk past it. It doesn't BSOD, shutdown, or dump anything as far as I can tell. It just restarts itself.
When it first started happening it seemed to always just stay on a black screen and the two case fans I have connected to the power supply (the other two are connected to the mobo) would start running super fast and would get somewhat loud.
I then disconnected and reconnected pretty much everything and straightened out the power cord which was coiled up and smashed up against the wall. The problem seemed to go away but then started reoccurring except it no longer just sits at a black screen with the two fans running super fast. Now it actually tries to reboot. Sometimes after restarting it freezes at different points during bootup (sometimes before POST, sometimes after POST, sometimes while it is loading windows, etc.) but usually it just restarts and eventually returns to the windows login screen (after going through the incorrect windows shutdown screen that allows you to choose between normal bootup and safe mode)
I have had it restart on me like 2 or 3 times while trying to plug in a usb device but other than that it only happens when I walk past it.
It seems to happen very randomly as well. I'll go a day or two without it restarting and almost forget about the problem then have it restart 2-3 times back to back while just walking past it.
I'm pretty positive it's not a heat issue as I have a full tower case and an after-market cpu cooler, and, like I said, it has never restarted while I've been sitting in my chair using it even when playing the highest demanding games I have for hours on end. The temperature readings I get right now are 28-32 °C at various locations.
As of yet, I have been unable to force this issue to occur. I can bump the case and shake it and nothing happens. I've ran it with the case sides off and wiggled each component but nothing happens.
Motherboard: ASUS M4A89GTD PRO/USB3
CPU: AMD Phenom II X4 970 Black Edition Deneb (3.5GHz)
Memory: G.SKILL Ripjaws Series (2 x 2GB) 1600
GPU: Crossfire Radeon HD 5770
PSU: Antec TruePower TP-750 750W
Case: Cooler Master HAF 932
HDD: Seagate Barracuda 1TB 7200RPM
CD/DVD: SAMSUNG TS-H663C/UOAH
OS: Windows 7 64-bit
I just flashed the bios with the most recent update the other day but that didn't fix it. There was nothing between the mobo and the case. I'm not sure what you mean about the monitor. It goes black like when you hit the reset button then displays all the start up information.
edit: it flickers off like it would when the computer is restarted manually. it actually still occasionally does that thing where it won't come back up. the monitor will go off and the fans and lights will still be on a running. and the fans connected to the psu will run super fast. but its like a pulse on the fans. they run at a normal speed for a couple of seconds then run super fast for a couple seconds over and over.
edit2: it seems to happen when the case gets a static shock. i have a pair of shorts that tend to have a lot of static. it restarts every time i walk past the case and brush it with my shorts and i can hear the static. it only happens when i brush the front panel on the case though. i'd guess that its the sub ports since it has happened before when i've been trying to plug in usb devices (i don't usually attempt to align it i just try to feel for it so i usually miss when the usb device first touches the front panel and the metal on the usb device touches the metal around the front panel inputs). it could be the entire front panel though.
i'd expect a static shock would be harmful and effect a computer in such a way but shouldn't the case be resistant to this? the only time i've ever had a computer restart due to a usb port issue was when i was trying to plug a live audio cable into my laptop and missed the audio port and hit the usb port instead. i've never heard of ports being so sensitive before. i mean i could always unplug them from the mobo but then i'm losing the functionality of my case.
edit3: Since I was able to pinpoint the cause of the resets, I was able to find information on the internet of other people dealing with the same problem. Apparently, Cooler Master will send out a front panel replacement free of charge without having to send in the defective one. I have sent Cooler Master an eRMA and expect this to solve the issue.