I know this is a weird question, but this happens to me. I’ll take a nap in class and have enormous burps right when I wake up (sometimes they wake me up).
The weird thing is that I don’t have to burp when I wake up in my bed in the morning or even after a nap on the couch. Does this have to do with the weird upright position that I’m sleeping in? I guess my main question would be what is the cause of these odd burps.
I am not a doctor, nor a nurse; in fact, I have no medical training whatsoever. In fact, I have only a vague idea of the positioning of the internal organs. However, I have slept through a lot of classes, so I’ll chime in.
I believe when you’re leaning over onto a desk, your normal breathing is disrupted and you end up breathing in a lot of air. I noticed this first during my intro to philosophy class freshman year.
This is pretty easily remedied by getting some damned sleep the night before class! This is your future we’re talking about.
It’s to alert your instructor that you’re awake now. It reminds your faculty to construct test items from the material presented during your nap.
This gets my vote for best preface to a post.
Welcome Louis.
Just curious… is there a fourth place you sleep as well or do you try and limit it to only three?
Well, at least he didn’t type IANADNANIFIHNMTWIFIHOAVIOTPOTIO 
critter42
As opposed to breathing in . . . what? Chlorine gas?
Just kidding, I think I know what you mean . . . swallowing a lot of air, right?
Though I wonder why that would be the case. Maybe you’re trying to swallow that puddle of drool that’s slowly creeping across your desk?
While you are sleeping your teacher is sneakily taking the opportunity to teach you creationism/evolution/republicanism/liberalism/Islam/socialism/astrology/[insert contentious subject of your choice here and stand well back].
You’re having trouble swallowing it.
Two solutions; inform your teacher that you are on to his/her evil plans or stay alert at all times during classes.