Nighthawk c7000v2 Connection Drop (ISP: XFINITY)

How is the Wifi Basic and Advanced settings configured on the modem? 

What channels are you using? Auto? Try Auto and 48 on 5Ghz. Or try setting manual channel 1, 6 or 11 on 2.4Ghz and 40 to 48 channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Does same thing happen with wired devices? 

What devices do you have connected to the modem? 

Please post a copy and paste of the modems connection status and event log page.
https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-modem-modem-router
https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-modem-router

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router?article=24311
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html

Only ISPs can update FW on C series modems. Some may have there own policy's that say they won't update user owned modems.