Edit: I just saw that the headline says without using the menu.
You could start Blender from the console with the default settings. Open the directory where Blender is installed and type
cmd in the address bar and press enter. Then run the following command to start Blender with the factory settings.
Next go to Edit > Preferences, wobble Resolution Scale, then set it back to 1.0 and click Save Preferences in the bottom left corner.
You can set the Resolution Scale in Edit > Preferences in the Interface tab. It should be set to 1.00 for the default scale.