1. In a vehicle radar sensor, a method for detecting radar sensor blockage, the method comprising: collecting sensor data using the radar sensor as the vehicle travels past stationary structures; generating a plot of normalized Doppler versus monopulse angle using the collected sensor data, wherein the plot includes a clutter ridge comprising points representative of the stationary structures, wherein the plot indicates signal magnitude at different points of normalized Doppler and monopulse angle; analyzing the plot to detect if the radar sensor is blocked by calculating one or more quality metrics for the clutter ridge, wherein calculating the one or more quality metrics for the clutter ridge comprises at least one of: calculating an average peak magnitude in azimuth, calculating an average variance of the clutter ridge in azimuth, and calculating average stability of peak magnitude in azimuth; and providing a signal to at least one of: a Controller Area Network (CAN) in response to detecting a radar sensor blockage, and a human/machine interface (HMI) in response to detecting the radar sensor blockage.