Had this same issue going on for a month or so, would be days with no issues but then most of the time was just the slightest lag with random DC's all day on whatever game
Called internet provider and they sent somebody out and ofc while they were there it worked perfectly fine so couldn't find anything but replaced the router and Ethernet cable
Next day immediately started doing it again.. had a 2nd person come out the following week and it of course again wasn't doing it at all
Nonetheless he ended up unplugging the router from socket it was in and put into a different wall socket saying it could be a lack of power in the outlet strip I had it plugged into
Actually seemed to fix the problem and it's been about a month of of no issues... Until last night (hoping just a fluke) but it's doing the same exact thing it was doing for that month or so it was acting up
I'm red barred on discord, but nobody hears the lag at all and I just get random 1-2 second click delays on RS the entire time / buffering issues on videos / disconnect out of no where but immediately log back in