GUNNY- why at 2AM????

Gunny (our Foster dog) is 8-ish years old small Saint that has a breathing/choking problem usually at about 2am. you are in your "GOOD SLEEP" and all of a sudden you are woken up by this horrible sound and it doesn't stop.  WHY at 2am???  What the hell happens that at 2AM the dog cant breath???  and is it that he cant breath???  What the crap is it????  I have sat with him but now I push him out of my room and tell him to go somewhere else to die (he's NOT going to die, he is just going to make that noise for a good 5-6 minutes so go somewhere else)  It's bad when Dave is waking up...Dave doesnt wake up for nothing....but it could be because I'm SCREAMING....GUNNY GET THE FUCK OUT.....GET OUT OF MY ROOM.  that might be why he is waking up :)