This has been going on for the last couple of weeks. At first it was very random and sporadic but now I can generally count on it happening once a day or so. He seems happy/eats/drinks water/crows/doesn’t seem abnormal otherwise, but this is very concerning to me . I am not sure what to search to get an idea of what might be going on. Anyone? I am happy to answer any questions that may help narrow down potential problems.
Yes, my rooster was doing this a month ago before he was diagnosed with tumors in his lower GI tract. He died last week. Yours may not have tumors, but he has something going on. I recommend bringing him to a vet who sees chickens for an xray. Here is a directory of vets - http://www.poultrydvm.com/poultry-vets.php
That is odd, the movement he makes about 20 seconds along in the video. How does his crop feel? Can you check it first thing in the morning before he eats or drinks to see if it is empty or full, hard, soft, or puffy? What do his poops looks like?