Well YOU sleep on a pillow (or two!), don'cha?
I have 4 dogs, and they all look for something comfy for a pillow. Lacking one, they scratch and fluff blankies or something to MAKE one. If all else fails, they're alongside me, using my leg or arm as a pillow.
I don't think it has anything to do with trachea problems exclusively because it seems ALL dogs do it, but it may make it a bit easier.