Yea, Yes, It happened to me, it still occurs every onc in a while, and like you, for no apparent reason, just sitting or even sleeping, I realised that this is happening 95% of the time due to bloating in the stomach, whitch happen to compress the lungs and make it so difficut to take in full breaths.
If I take ENO, the burping helps a lots, and I'm back to breathing ok.
rolaids work, but not as good.
whed Doc's check, they find nothing, now I take Nexium for the stomach, and it seldom happens now. good luck.
It might be worth trying to get pulmonary function tests while you are having the symptom. It may be vocal chord dysfunction which is similar to asthma in symptoms and they can trigger eachother.
Try using a peak flow meter with and without the symptoms, if the peak flow doesn't drop then it is likely something other than your asthma (which also makes sense if the inhaler doesn't work).
I dont know if its even close to my issues but I just found out I have severe allergies and one side affect of me eating chocolate is a hard time breathing. It felt like someone was sitting on my chest. My Proventil doesnt work. I've been off chocolate for a month and I can breath sooo much better. Worth a shot. Simple blood test.