Happens to me too. Just got XFinity in November and at least once in the morning and once in the evening, the modem loses its downstream WAN address for 6 minutes. I know this because I have a particular device that notifies me when the connection is dropped and when it is reestablished.
Note that we have learned to just sit and wait. Rebooting does not accellerate resumption of services.
To Comcast's credit, one tech in particular has been very helpful working with me at the house and has told me that there is a trouble ticket for my street as I am not the only one with this issue. The technical term for what is causing this is a "S u c k o u t". <---the posting filter won't let me type the word.
No idea if it will ever be fixed, so I basically dropped Fios's slower but completley robust internet speeds for Comcast faster and more modern product, which drops out twice a day.
@Hay72 wrote: My xfinity WiFi/Arris gateway disconnects everyday ...
Can you connect with an Ethernet cable? That would allow you to determine whether the problem is the Wifi signal or the link between your equipment and Comcast's network. Network connection problems that affect both Ethernet and Wifi devices are often due to poor coax connections, usually in or near your home.
If you want to troubleshoot this yourself, please see Connection Troubleshooting Tips. If you still need help, please provide Information Requested for Connection-Related Posts, especially downstream power levels and SNR, upstream power levels, and error log.
If you can't find the problem or you'd rather have Comcast take care of it, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. If they can't fix the problem remotely (unlikely), insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device, or anything outside your home, you shouldn't be charged.