As I wrote in a different thread here last night, it is a good idea to reboot one's router/modem at least monthly (including devices connected to it) to eradicate any gremlins causing known and unknown issues.
I, too, have Comcast, and it rarely goes out. When it does I can tell because both wireless AND wired devices stop working.
Most issues with wireless devices are because of less than optimum placement of wireless device relative to where the router is located. A device like an Echo is most always sitting in the same place, and most of the time it can work fine. But, wireless strength is ever changing, and if it drops below a certain level for even a moment an Echo can loose the wireless signal.
The solution is to get the Echo (or any wireless device) closer to the router so signal strength is consistently stronger. In my case, my Echo is downstairs and router is upstairs so the Echo and Chromecast etc. located downstairs need a little help in the form of a Wi-Fi range extender downstairs directly under where the router is. Bingo, a stronger Wi-Fi signal downstairs. I use two range extenders; one for 2.4G and one for 5G signals. Although my router is one of the top-rated ones, it is a big enough house and range extenders are necessary to eliminate or lessen weak Wi-Fi signal areas around the perimeters of the house.