Do I have a virus? Somewhat frequent hard shutdown

Could I have a virus that Norton is missing. I've been having spontaneous hard shutdowns for a couple of months.  The weird thing is, on the days that it happens, it happens at approximately the same time, between 10:37 and 10:40 am.  There are no tasks scheduled for that time. Nothing in the event log.  I'm at a loss :smileysad: