How many different browsers have you tried?
Does the same thing happen in different browsers?
I had a very old computer and it was getting bogged down but I started using Chrome (it was faster) - then I have this new one and I still use Chrome - much faster than IE and FF.
Cool thing about chrome - you can right click at the top tabs and delete running programs with a quick task manager - I watch a bunch of videos and that slows down the puter.
This slowdown has only been recent. I don’t use different browsers.