Anyone have any ideas why my internet keeps dropping out?

It’s been doing it for a couple of months. It started with our old computer. Well, we got a new computer and we changed providers, from ATT to Cox. But it still keeps dropping out. We disconnect the router and then sometimes it works. But other times, “whoop!” It’s just gone. Sometimes it comes back right away, other times it’s gone for hours.

We’re bringing Cox in next week, but I was just wondering if there were any geeks out there who might have an idea of what is going on.