I am having the exact same issue. It's been going on for ~2 weeks now.
Sporadically through out the day my internet connection will reset. I've confirmed all of the physical connections are firmly in place. I've reset the modem, as well as the wifi mesh too many times to count. None of the times have made any improvement.
The modem does not appear to be the problem, all it is doing is detecting that the upstream network is not connected.... multiple times throughout the day.
The outage map is showing 5 outages within 2 miles of me. Either Comcast is fixing a lot of little problems, or they have yet to track down the cause of a widespread problem.