If your connection is strangely slow for long periods, investigate why

There are countless factors that can slow down a network connection, from failing infrastructure (both in and outside the home) to bandwidth leaks to unauthorized users sapping your connection from outside. If you frequently experience slower-than-normal internet speeds, go into your router’s settings and look for possible causes.

If you suspect the problem isn’t with you but with your ISP’s external infrastructure, call them. They should be able to run a test from where they are. If they detect a problem, they’ll usually fix it rapidly and without charge, since it’s likely to affect a large area.