Are you yawning at me?

Today's odd observation: a Buick was tailgating me almost entire way home. Finally, a mile from house, we came to an intersection with, and he pulled up next to me in the right turn lane. As I looked to the right to check for traffic, he was looking at me and yawning with a giant yawn. Was he getting sleepy from driving so slowly? Was he trying to tell me something? Or was he just tired from a long day at work? Whatever it was, it looked very strange.