Originally Posted by pe1chl
This is probably a "service" from your window manager, not something that has to do with nvidia-settings or the X server config.
Some window managers remember te resolution and think they are providing you a good service by setting it back.
It's NOT the window manager. It is the settings daemon loading the res from the config, or the session manager running a program that restores the resolution from a file saved in one of the user's homedir (one of the hidden dirs within it).