I am using a Netgear WNDR3700v4 as provided years ago by Charter.

I am using a Netgear WNDR3700v4 as provided years ago by Charter.

After years of having to reboot the Netgear router in order to connect , reconnect or have the router listed as a wireless option, or restore internet connectivity; I managed to greatly reduce the problem.  I have not read any comments that a device available to the router could interfere with other devices connecting wireless to the router, but this appears to be the case.  Years of usage suggests that a wireless Roku 2 model 2720X being idle but not logged into the router was causing problems for other devices to log in or relog into the router.  Perhaps other idle devices serviced by the router could cause problems as well.  This does not directly address the speed issue, but it could since it appears the router can somehow be compromised by some issue with an associated device.  Could I suggest unplugging other devices one at a time from the network to see if the problem clears up.