Mine will hiss at times, sometimes a whole lot. It was mainly during handling. I kept ignoring it and would hold for a few minutes after the last hiss. I did not want to condition the snake to equate hissing at me as a way to be put back in the cage. I would expect it to be whezzy or popping sounds if RI. If in doubt consult a vet. Respiratory problems can be bacterial or parasitic in nature. Make sure you are keeping proper temps and humidity. Try picking the snake up and see if this elicits the sound. If so it is probably just hissing in an effort to scare you.