Can you hear any noises coming from your beardie or see any signs of discharge built up anywhere? It could be an upper respiratory infection and in that case you need a vet.
And yes they can cough. Rex did that when he had an uppper Respitory Track infection. Get to your vet ASAP if vertical sleeping and or wheezing. I could hear it up next to my ear.
I just set Swordtail's timer for his bath and paused it so I could actually fill his soaking bowl up and he crawled over my phone and canceled the timer
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!