I don't know what ISP you have, but do ask if ANY changes have been made in your neighborhood "recently".
That is a question I didn't think to ask when I had a problem...
I had a similar issue a while ago where my internet to slow to a crawl every evening (and weekends).
I had the top of the line DSL package at that time, and it would slow to speeds at or below dialup.
Every ISP department/group/tech checked everything for MY DSL
and said everything is fine with THEM - it's YOUR
The ISP said the issue is MY HOME wiring
, and even had technicians here seeing the problem, trying a new modem, re-wiring, ...
I said "How can this be?, it works fine until the evening...MY MOME wiring does not change at night!"
The tech in my home that saw the "evening slowdown" agreed with me...and told the "ISP Guru's" so...
FIBER OPTIC cable had been added to my neighborhood sometime before this saga started...
So I finally said - OK switch me to FIBER OPTIC and if the problem is not fixed I'll switch to another internet service provider.
Well, the tech that came to install FIBER OPTIC said to me "FIBER OPTIC does not work at YOUR HOUSE
I asked why, and was told "Not sure now...we may have to dig up lines to find the problem!"
It turns out it was a wiring problem in a "neighborhood box" when FIBER OPTIC was added to the neighborhood...
The problem for me didn't start when FIBER OPTIC was added to my neighborhood.
It started when someone else in my neighborhood signed up for for FIBER OPTIC internet!
Sad but true story