Pins and needles at first. Then one night the whole arm goes completely numb, "dead weight you have to pick up with your other hand." For most guys it starts every few nights, then most nights, then every night.
Most men assume it's circulation getting cut off. It's not. When the pillow is too short for the shoulders, the head drops sideways and tightens a nerve corridor in the neck that's only 10mm wide. Squeeze it and the arm shuts down.
Match the pillow height to the shoulder width and the corridor stays open. The arm stays alive. 💡