Bearded dragon making a pudding/coughing noise? Help

I just bought my first bearded dragon today from a seller on Craigslist. Before that throws any red flags these people seem to genuinely care for their beardie and he was in great shape. Strangely i noticed when i got home he was making some sort of coughing sound. A small breathe of air compressed type of sound and his beard would puff out a little bit “ not sure how to explain.” It has me semi worried because he’s such a great beardie and i want him to be healthy. I’ll list some things about the setup/beardie that may lead to a issue. He is 2 3/4 years old, about 17 inches in length, normal weight, did have 3 nails missing from front right hand foot. His setup is a 40 gallon breeder 32x18x12 150 watt basking light “ non colored” a t8 uvb light fixture i believe, a medium sized water bowl on the cool side of tank. Some fake plants and a spot to bask and a spot to sleep. I’m stressing a bit because of course with my luck a problem occurs the day i get him ?. Please someone tell me what i can do to solve this problem and possibly what is causing it. It would mean the world, thank you. Btw beard isn’t turning black and the cough is pretty faint just a forced breathe of air, i noticed it about 6 times throughout the entire day. Am not using loose substrate either

They do that occasionally, especially after a meal. Keep an eye on him though and if you see increased mucous around the mouth, nose, or eyes it may warrant a vet visit. In the meantime I'd just make sure the lighting and temperatures are all fine tuned for him. How old is the T8 UVB light? How far is it above the basking spot? If it's more than a few months old, it may be time to replace it and I'd invest in a higher powered T5 light.

What are the surface temps across his enclosure? You'll want to be sure he has a good gradient set up with the basking surface at around 100-105 or so and the cool side surface around 75-80 with a gradient between.