Apple TV connection issues

I've had difficulty with Apple TV connectivity. I have Xfinity broadband, a Netgear R6200 router ethernet connected to Netgear N150 router (required by my Xfinity alarm system), and a Surfboard modem. When I turn on my AppleTV, it and all of my other devices (2 iPhones, 2 laptops, Harmony Hub, alarm system, DTV) will not have internet connectivity for a few minutes. My modem and router still have all the same lights on. My Wifi connection is 5 bars. If while I'm watching Apple TV I use my phone, for example, the Apple TV stream will stop. I have >20mbps on speedtest. I got a 4th gen Apple TV hoping that would solve the issue, but the problem remains. I don't have any internet problems when not using the AppleTV. I assume this is a router issue? I've tried fooling around in my R6200 settings but don't know much more than basic settings, which all seem to be fine. Is there anything specific I should try? Should I just buy a new router and cut my losses? Any help is appreciated.