Countdown timer is usually from the windows shutdown command, is that what you saw? Need to get the exact message posted. Could have been an update that was done that needed a reboot, or someone send a shutdown command to your system remotely, can't know withoug the exact message.
If you suspect you may have a virus, it's a good idea to run a scan with a couple of programs. Download the recovery boot CD from Avira, run the scan with that and see what happens.