This happens even if I disable all the extensions, but I think I found the culprit. There are two processes that take the whole CPU up together, one of them is probably the browser, since everything crashes if I kill it. The other one is... something. I checked the process name for it and it's this: Pastebin link since it's very long
I can kill it and the browser will still work, so nothing important I guess. And if I kill one, the other stops using up CPU too... Strange, but at least there's a workaround for now.