Hi - this happens to me all. the. time. It drives me crazy - I have found that yawning is the only thing that makes me feel like i am getting enough air in my lungs. This mostly hits me when I'm driving - I can't tell you how many times I have been embarrassed when I pass someone I know on the road and they are looking at me strangely because I am idiotically yawning. I have also found that slowly breathing in, holding it for a few seconds and then exhaling thru the mouth helps.