Well it isn't normal behavior and his breathing is also labored. A few things come to mind, but mind these are obviously just theoretical guesses.
Since you just got him in there could have a been an injuring causes a neurological disturbance. He could have swallowed a bunch of air which causes issue, I can't remember the exact medical explanation.
He could have also ingested a rock or something causing a blockage. Not knowing how long he was before you got him, it could also be a nutritional defiencency, likely vitamin B1, which is mainly caused due to feeding foods high in thiaminese.
Course of action is another story, the only one I know how to deal with would be the nutritional defiencency, by feeding proper foods. Some of the other like a blockage or air, may just have to work itself out. Raising your mg to about 1400ppm may help with digesting and passing any blockage. An injury I guess you would just have to hope for the best.