Repeated "Restart required". I suspect phishing

I've got Norton Security With Backup.   It automatically updates frequently.   Today I started getting a popup message every few minutes saying "Norton LiveUpdate Restart Required."  (See attached screenshot).  I didn't click "OK" because I suspected phishing or worse.  I checked my Norton, it said "You are protected.  Protection Updates: Current".  And then I cold-rebooted my machine.  The popups continue.  This is either (1) a bug in Norton, or (2) a sophisticated-looking phishing expedition.  Please advise.