Short intermittent service dropouts in both internet and TV, why?

I am experiencing 2-3 second dropouts where a blue screen quickly appears and disappears with a message starting Unrecognized or Unauthorized.  Service returns as nothing happened.  The internet seems to recover without disruption, only a few lost packets.  Streaming (any service) and Xfinity TV show the same error screen.  I have a new STB and it continues to occur.