When I work with clients, I so often find that they don’t close all the individual windows that have been opened. They get opened by clicking on the icon or menu option for a task, and then another, and another....
One way to see how many windows are open is to select the Window menu option, which gives you a list of some of the open windows. There are people that will have more than 10 open, so this list is not all that helpful.
Another option is to use the Open Window List feature. Select View and then Open Window List. This opens a sidebar on the left that will list all the open windows, listing the most recently used window first.
What about when you close the file? If the file is then closed with all those windows open, they may remain open when the file is reopened, based on the preference set. If so, it will take a very long time to load as the file is trying to bring it back to the state it was upon closing.
The solution.... close your windows when you leave. --- Window -> Close All