DIAGNOSIS You're experiencing intermittent mesh instability. This is often caused by wireless backhaul interference (if your Points aren't wired) or a conflict with your ISP's modem/router.
FIX First, ensure your ISP modem/router is in true bridge mode or that you've enabled IP Passthrough/DMZ to the Nest router. A double NAT or two DHCP servers fighting can cause these drops.
IF THAT DIDN'T WORK Change the mesh channel. In the Google Home app, go to WiFi > Settings > Advanced Networking > Wireless Channel. Switch from "Automatic" to a specific channel (try 1, 6, or 11 for 2.4GHz).
HEADS UP If you're using wireless backhaul (Points not connected via Ethernet), dense neighbor networks, baby monitors, or microwaves can blip the connection. For stability, consider running a single cable from the router to one Point to create a wired backhaul.