I've been dealing with this off and on for 12 years. My symptoms are very much like most of the posts -- an urge to take a deep breath but unable to get it, trying to yawn but can't, finally getting a satisfying breath after several attempts and then going through the whole thing a few moments later. I get "bouts" of this for a few days and then i'm fine for a while. Sometimes i'll go months without any trouble. It happens at different times during the day, and, when i'm having a bout, it's certain to occur at night when I lie down to go to sleep. I'm fairly certain it has nothing to do with stress, as it's happened to me during both stressful and easygoing periods in my life. I'm otherwise very healthy, and my lung capacity hasn't decreased since i've had this problem.
Some of the theories included in these posts are interesting. There's been some mention of low blood pressure, and i've been considering that one. I'm a runner, and my blood pressure seems low at times (i get dizzy if I stand up too quickly). And, it seems that my bouts have not occured during times that i've laid off running and gotten out of shape. But the bouts are too intermittent to say for certain. Also, i've had the breathing problem at various stages of rest and exercise, so it's hard to cite any physical trigger that the low blood pressure would be causing.
The allergy theory could be valid. I considered a food allergy, but after tracking my diet for a few weeks I didn't see any real link. The literature on food allergies has a lot to say about a relationship between breathing problems and peanuts, and there are traces of peanuts in a lot of foods. But I didn't notice much of a correlation. I'm able to eat straight peanut butter without a noticeable reaction. I've never given up coffee, but i've had many weeks of clear satisfying breathing while still having my morning coffee.
I have cats and a dog. But I had this trouble long before I lived with any cats or dogs.
Then there are environmental allergies. This is probably the most realistic theory. I've had this problem in almost every season, while living in the south, the desert southwest and the pacific northwest. Just the same, molds and pollens are everywhere, at most any time. And my certain nighttime bouts could be explained by pollens and/or mites staying in bed linens. I've never been to an allergist, but I may give that a try one of these days, but i'm not expecting that to show much. Then there's the industrial pollution angle. I suppose this could be. I've lived in cities since i've had this condition, so it's hard to tell. I do remember the problem going away last summer when I spent a week at the beach. But the vacation also took me away from stress, my bed linens and my regular diet. And it could have been coincidence. My bouts do fade away after several days.
There's been one mention of lyme disease. I haven't researched that one yet, but the idea of it is interesting. I'm going to check it out a bit further.
Thanks to all of you who have posted. It's good to know that you're out there. I'm sure that if we keep exchanging information we'll get on the track to figuring this out.