Thanks for your prompt reply!

I think I figured it out. YEAH

I hooked up a 2nd computer with a wired connection and started Ping Plotter on that one and guess what - no red bars. Red bars still appearing on the Wifi connected laptop during the same time period and the cell phone blinking on and off the Wifi.

Then I used the WiFi Analyzer app on my phone and noted that the channel my router was using was close to a couple of other routers. I have adjusted the channel in the past to miss other local routers but I think my router or theirs must change occasionally. I think this must happen a couple of times a month as we have been having this problem off and on for quite a while.

I changed the channel about 2 hours ago and no problems since then!

See the attached data file of the laptop on the Wifi. The gap at about 2:40 is where I changed the Wifi Channel.

Ping Plotter helped me pinpoint the problem and then verify the solution.
Thanks!