I had a concussion over 4 years ago and now seem to suffer from shallow breathing when sleeping which wakes me up 2 or 3 times a night. I also experienced waking up gasping for breath a year or so ago which was not nice, which thankfully it passed. I used to find myself waking in the same position I'd fallen asleep in which is weird and not normal, I think I was tense. I think it's related to residual anxiety from the concussion and not being completely relaxed. I notice my sinuses seem to be restricted when I lay down for a period of time too.