I can add that is seems like the freezes have become longer. A recent freeze (opening a new window) lasted approx. 40 seconds. As the OP said, it gets tired real fast.
I also get freezes. I don't have any extensions installed. Fx. it may happen when opening a new window, or by clicking on a bookmark folder. Firefox freezes for several seconds.It began in recent history (a couple of months ago?)Windows 10
