RISK alert, requires restart

For a month now  I have gotten daily pop-ups "ALERT-RISK REQUIRES RESTART".  I have restarted  2 and 3 times a day and have run Power Eraser several times.  Next day, or an hour later, the Norton Alert box comes up again with the same Restart demand..  All scans I do show "safe" and "all risks handled".   What is the answer to getting rid of this bother.  Is it really indicating a risk?