Having the same issue. The past few days have been terrible. Every 10 minutes the internet drops. Can't do conference calls, can't stream videos.
Finally got through to US support rep (all reps in Philippines are shelter in place and can't work form home). She said Comcast had been rolling out router firmware updates across the nation and this has caused some issues with connectivity.
She had me:
1) disconnect coax from router
2) disconnect coax from wall
3) reconnect coax to wall
4) reconnect coax to router
5) unplug power to router for 20 sec
6) plug back in power
That has at least led to much better connectivity for us. She said that if the issue comes back to go to My Account and request a new router be delivered.