MS Windows could really use a "WHAT THE HELL ARE YOU THINKING ABOUT?" feature. From the first version of Windows with networking, a Windows install had a lifespan of a few years, after which simple things like clicking on the Start menu would take several seconds to respond. You expect this when connecting to an external disk share, but it was woven into the OS so that it happened at weird times.
I didn't know enough about Windows internals at the time to figure out why this was happening. After a few days/weeks/months of irritation, I usually ended up doing a fresh install and re-installing/configuring all of my apps.
Just in the last month or so, my Windows 10 development system will sometimes take several minutes to pop up a File Explorer window. Default File Open/Save dialogs are affected as well. I'm not using any shared drives and I disabled the stupid One Drive thing. At this point, a reboot resolves it, but I sense another reinstall in my future...