Stomach randomly squeezes in for no apparent reason...?

It's like when you suck your stomach in to look skinnier, but it only happens at night and I don't try to. I think occurs when I inhale whilst breathing perfectly normal at random times.i do have asthma in the red zone, I was born with it, but its never really done anything, I have a lot of endurance, but I tire out easily due to my being generally weak in the muscles and laziness. I've never had an asthma attack, and I don't really know what wheezing is but I don't think I've done it. I do catch hay fever and have seasonal allergies and the only food I'm allergic to is black beans.

If you have any idea why my stomach is randomly sucking itself in during the night, please do share. I googled it and can't find anything.