Hello saurabh50411

                                    We understand that you are having intermittent connection issue on Wi-Fi, and also you have tried all possible trouble shooting like restarting modem already no need to repeat again. Basically,  If other Wi-Fi sources such as neighboring wireless access points are using the same wireless channel, this may cause intermittent connectivity issues, even if the competing signal is relatively weak. Changing the wireless channel within the  gateway can improve connectivity. so I would suggest you to try changing Wi-Fi channels 
will avoid interference and that will give better speed and connection. You can check the article for reference to change the Wi-Fi channel using the below link.

                                 http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Changing-the-Wi-Fi-Channel

Let us know if this helps.

Potentially we could help you if you gave us more info on what the actual issue is and what you’ve done trying to fix it. 

Details are key since we’re not there to see whats going on

Everything I have done. If you unplug modem and plug back in then start working but then after two or three day  start same problem and need to do same process again. 

even I am not getting full speed. My Comcast speed 300mbps but Wi-Fi give me 89 or 92 also I bought Wi-Fi 6 MR60 nighthawk that make more speed still modem issues going on and reboot again and again. I am tired I like to return this

What hardwired speeds do you get from the g36?

Do you have a screensnip of the cable connections page and the event logs. 

This is the speed right now I am getting before I had Netgear modem and it’s gave me 400-500mbps but now this is all time dropping speed and need to reboot many time

I need to talk directly on phone call. It’s hard explain all stuff here

Some time gave me less then 100 speed when dropping internet 

How can I return this modem? It’s good idea to buy new one

It’s still under warranty 

fluctuating speeds and internet going in/out tend to indicate line issues. You haven’t shown the cable connections page or event logs. But feel free to contact support. 

https://arris.secure.force.com/consumers/ConsumerProductSupport#