why do i have to unplug my modem every time i want to use my xbox for it to connect?

New internet customer here and every time i turn on xbox one x it is never connected to the internet as it has always been with my previous isp. I have to physically unplug the modem then plug it back in and wait. After several minutes it will connect and stay connected. That is until I turn it off (or stand by). I am hardwired to a netgear cm600 cable modem (brand new). Nothing else is connected to this internet.        I also have the same problem i read about on here with getting my 300 megs download but only getting 2.5 megs upload instead of 30 which I am paying for. This only happens with the xbox but since the xbox is the reason i got this internet and there doenst seem to be any fix for the problem, I dont think i will be keeping cox service very long