Around 4 o'clock yesterday morning, my desktop went into a crazy loop. I had turned it off the day before around 5 pm, nothing special happened. At 4 am, it started booting up and shutting down automatically during a few minutes, until I got up and unplugged it. When I plugged it back in in the morning, it went at it again. I pressed the start button, then the delete button until I got to a blue screen with several options, then pressed escape to let the system finish booting up. After that, I updated my antivirus (ESET NOD32) and Anti-Malware, did a scan with the one, then the other, and the computer appeared clean. I then worked all day long with the computer, no problem. When I shut it down, it went into the loop again. This morning, it won't boot up. Whenever I press the start button, the process is interrupted after a few seconds. I will keep trying, but my question now is : should I consider this as a virus or malware situation, or as another type of malfunction? I am very confused at this point and do not know how to tackle this problem.