Increased respirations and panting can be the result of being overweight, fever, thyroid conditions, hot weather, pain, lung disease, and adrenal gland disorders like cushings disease. Since the panting does stop during sleep it makes me wonder if he is not suffering pain from arthritis which is worse when he is up and moving around. If he is slower getting up, reluctant to move, stiff, or limping occassionally this may be an issue worth looking into. There are pain medications prescribed by a veterinarian that can result in significant improvement as well as a supplement called Cosequin DS. Since panting can be the result of several health issues it wouldn't hurt to have an evaluation by his veterinarian. The vet may want to perform bloodwork before starting anti inflammatories. If you feel this is unrelated to pain and would like information about any of the above topics please feel free to write back.