"Preparing your desktop" is only shown when logging in to a new user account first time. User folders are not created when you make a new account, they are instead only created when new user logs in first time. Seeing this text means Windows is creating the folders.
In your case, seeing this can IMO only mean one of these options: either you were accidentally logging in to a new user you'd created, instead of your normal account, or that your user profile is corrupted.
Microsoft article tells how to fix a corrupted user profile.