There may be an option in your browser control to stop the popups that obscure a page - I don't think they are supposed to do that. There is probably a setting to delete all cookies when you close down for the night too, except any that you have marked to be kept. If you can't find how to, get Ccleaner and run that every few days. That deletes all kinds of stuff that could be clogging up the memory as well as cookies, temporary internet files, and so on.
You could also scan your machine for malware using Malwarebytes. There may be a sneaky little addon in there that lets the popups in by the back door in.