Something is loading or running in the background and bogging down the processor which is why you get that beachball. It is really no different than that of your PC and its 'wait' cursor.
You can use a task manager or sorts to see what is really running in the background and then would be able to tell what exactly is causing the issue. I personally use MemMaid and it will tell you what the process is and how much CPU it is using.
