Lack of driver alertness is one of the leading causes of traffic accidents. In this work, a coherent FMCW radar was used to observe the Doppler and range signatures of various head motions. The Doppler and range information was analyzed using range-Doppler evolution, and the Doppler signature was extracted from range-Doppler evolution to create a Doppler spectrogram within LabVIEW. By analyzing the range-Doppler and the Doppler spectrogram in different head and neck motions, Doppler and range characteristics of dorsal flexion of the neck, the motion that indicates low driver alertness, were distinguished from those of other driver head and neck motions. Ultimately, experiments demonstrated the potential of radar-based head motion detection as a driver monitoring solution.