I sometimes find myself yawning as I drive home from work or after the gym. I don't feel drowsy, yet I can't help yawn. YAWN! Excuse me. (I bet I made you yawn too.)
There might be an explanation to yawning. According to a study led by Andrew Gallup from Princeton University, yawning helps cool down our bodies--particularly, our brain.
Gez, all these years I've thought there was an odorless gas filling the interior of my car slowing killing me. In reality, it's just my hotheadedness.
Sources: "Does Yawning Cool the Brain?" Austin Awakenings, February 2012, Pg. 12; http://www.princeton.edu/main/news/archive/S31/64/49G23/