If you are in a car or a train where there is no place to pray and you cannot stop and pray at the side of the road and the time for that prayer is running out, you should pray in the best way that you can, even if you are sitting in your seat and even if you are not facing the Qiblah.

Yawning is from the Shaytan. If you yawn while praying, you should resist yawning, cover your mouth and suppress your voice (not make a sound).