Should I prop up baby's matress on slight incline?

I noticed that my 2 1/2 month old son occasionally sounds congested in the
morning. We live in the northeast U.S. about 20 miles north of
Philadelphia, where the pollen is horrible. I myself have been congested
since it is springtime. So my guess would be that it might be the pollen.
It's nothing too severe, and we're going to take him to the doctor
shortly where we'll ask about this situation.

I've also read that one theory regarding colic was that it may be caused
by GER (Gastrointestinal Esophageal Reflux), i.e., acid washing back into
the throat of the baby.

So, my thinking is, place blankets under the mattress so that it's on a
slight incline. Has anyone read anything on this? It seems to make sense
to me because I'd always been told that if you are congested, do the same
thing, or prop yourself up on pillows.