D.L. Johnson,
Thanks for the reply.
Checked login items -- all were legit.
Ran an old malware checker I had. Scanned 100,000+ files (see next item) with no problems id'd.
Downloaded Malwarebytes and ran it in free trial mode which used the premium options. Scanned 74,000+ files (Not 100,000+ ?). Found 16 infections - all of them Adware. I found in the problem report BrowserActivity.service.plist in 2 libraries. I quarantined all the infections and restarted. Hard drive worked for quite awhile after restart so I started Activity Monitor.
I found the BrowserActivity.gqa process running whose user was root. It was the topmost process in the Network tab receiving and sending packets. If this is a root process I guess it's OK because, if root was compromised, I'd be seeing much worse problems.
Perhaps the plist for BrowserActivity having an adware problem caused the odd pop up windows. We'll see if I get anymore pop up windows.
But I consider this issue solved for now.
Thanks for your help. CLee