Spinning beach ball problem

I was also having this problem and found the solution by properly managing my Firefox Extensions. Even if you have a good reason to have a lot of them, you probably don't need them all activated at once. I went through and disabled all but three. One of those three was a "legacy" extension which had not been updated in a couple years. So, I found and installed a suitable replacement and not only disabled it, but deleted it. That did the trick and the annoying spinning ball went away. You should begin to get rid or replace any extension labelled "legacy" anyway since Firefox 57 (due out in November 2017) won't support them. The reason this is happening is those old extensions were built with an old framework which required the developer to constantly up date their extension in order to stay compatible with each subsequent new release of Firefox. The new framework ensures forward compatibility much farther into the future.

Also take a good look at your Plugins. Do you need all of those active at once? I disabled one of those that didn't have any effect on the spinning wheel, but the point still stands: I don't need it everyday. So, it's disabled

A Spinning beachball happens when the application is not taking events from its event queue. Events are things like your mouse clicks, keyboard usage with the app, etc...

So the question is why does Firefox get some busy doing something else that it is not paying attention to the event queue?

Do you have Firefox Add-On's (Firefox -> Tools -> Add-ons)

If you do, try disabling them, as one of them may be causing your problems.

Firefox spends most of its life accessing the network, so if there is a hang attempting to access a web site, it could cause Firefox to hang waiting for the network to respond.