Take it to a vet ASAP. breathing difficulties in a kitten (or any small animal) can turn fatal at very short notice. Keep it quite and minimise stress on the trip, in a cat carrier keep it in the dark.
Take it to the vet. In the meantime, make sure it is comfortable but also getting plenty of food and water. The animal may have asthma or something wrong with the lungs.
Keep the kitten in an area which you can make the air moist with a humidifier to see if that will help it. It could have a hairball obstructing its airway too.
