Sounds like your router is trash, or your Beam is defective.

Before you investigate further about your router or Beam being defective, try powering off  all Sonos devices, restart your router and wait until the router is back before powering up Sonos.

I had some issues when I added the Beam. I made it my wired root zone and everything is rock solid.

Hi,

Did you try to assign your Beam a static (reserved) IP address?

It could help resolve the issue if the disconnection/reconnection is due to the DHCP lease expiration and inability to your setup to renew it (likely caused by the router, unlikely a defective Beam).

Alternatively, to confirm the DHCP root cause, you could instruct your router to increase the lease time significantly and see if the problem occurs at the same frequency.

This answer is way over my head!  Thank you for taking the time to explain but I don’t know how to do all that you suggest.   

I did unplug both router and modem. Turned off all Sonos products.  Plugged in router & modem, turned on Sonos app and there were my two systems (Sonos 3 and a Beam). I just don’t want to go through this every day.  I am on a 5G network.  If this happens again tomorrow I will return the Beam otherise I will have to hire someone to come and get this all to work consistently costing at least $100 if not more.  It’s just not worth the hassle. I have other products that I can use in my house that just aren’t this complicated.