My cat is breathing heavy and makes hairball noises without coughing anything up. What could be wrong?

My cat is taking what appears to be unusually deep breaths. You can see his stomach move in and out when he breathes. He also has been making sounds like he is coughing up a hairball, usually lasting around a minute. He never coughs anything up, however. He has been doing this for a long time, though, and it hasn't seemed to affect him, however, it is getting more frequent. He eats, drinks, and plays regularly, and doesn't show signs of being sick or slowing down. What do you think this could be?