How to identify applications and DLL which are slowing the File Explorer

As booting in Safe Mode fixed the problem, this indicates that some third-party application is responsible for this.

To locate the problematic application, you may use the free tool Autoruns for Windows.

This utility shows all programs configured to run during system boot or login in its "Everything" tab. You may turn off startup items with a click and return them later with another click. You may avoid listing Microsoft products by using the menu Options > Hide Microsoft Entries, Hide Empty Locations and Hide Windows Entries

I would suggest turning off startup entries in bunches, drilling down to the startup program that causes this behavior. Once identified, it might have some setting that can avoid the problem, or can be uninstalled.