I'm unable to see the video. Can you post it to a sharing platform like vimeo and post a link? I'll be glad to have a look at it and let you know what I think.
Oh, and I should have said this in the beginning: this happened right after Godzilla ate a few crickets. He ran up to his basking spot and started doing this. I am sure the crickets weren't too big.
I guess my mind is being all stupid from potential Dragon-Parent-Worry. Heh.
Oh. Burping! I never thought of that. Haha. It doesn't happen very often at all. However, for the past week or so, our upstairs air conditioning unit hasn't been functioning, so the humidity in his tank has been higher than normal. I added in extra moss this morning. I just took a look at the three humidity gauges in his tank to get a good average (they're all analog, have to get a good digital one still.) Looks like the average is about 45. A little high, but much better than it was yesterday.
I wouldn't use moss but if the gauges are accurate, then 45% isn't too bad at all and shouldn't cause issues. If you're thinking respiratory infection you'd want to look for excess mucous in his mouth or bubbles from his nose along with regular coughing or burping behavior. Since this isn't frequent, I'd guess it's more likely harmless indigestion/burping.
All my pet lizards do that kind of wriggle sometimes after they've eaten, and I've seen wild lizards do it too.
Also the little chewing actions seem to me to be the lizard masticating some food it returned to it's mouth.