The present disclosure relates to a method for operating a motor vehicle. At least one breathing movement parameter describing an upper body movement of a user of the motor vehicle and a driving movement parameter are detected, using a sensor device of the motor vehicle, and a breathing signal and a driving movement signal that describe how the parameters are generated. A vitality parameter that describes breathing of the user is determined on the basis of the signals. An evaluation and control device of the motor vehicle ascertains a reference value range of stored, user-specific reference values of the vitality parameter, a determined value of the vitality parameter lying in said range, and, on the basis of the ascertained reference value range, a driver state index is determined. A control signal for operating a driver assistance device of the motor vehicle is generated as a function of the determined driver state index.
