Thanks everyone. We will be following up with his Doctor. In the meantime, he is on nightly Singulair (for allergies, and I think it reduces inflammation in the airways as well). He also now has a rescue inhaler, which we will use before bedtime as needed. He's working on the hand-breath coordination required for using it

He's a little trooper.
He has never had a problem with this before moving here. We do not have AC in our trailer, and I am almost certain the humidity is part of the cause (or trigger). I have a lot to learn about this, but I am certainly going to get him the best treatment possible.
My first thought when he started having these symptoms at night was anxiety (he felt like taking deep breaths), because he was called the "N" word at his after-school program. That is why I wasn't thinking about other causes until recently. Thank you so much for your help.