Yawning is an involuntary reflex, and if you are concentrated on it, you may not be able to yawn. If you have throat obstruction or breathing issues, see your doctor.
My first thought is that you should contact your physician. This can be a normal thing, but can also be an indication of an underlying respiratory problem.
Yawning is normally a sign of tiredness or sleepiness, so more than likely if you were to go rest it would stop, or maybe try to get more sleep at night so you are not tired during the day.
