My Dog Breathes Heavy And Fast While He Is Resting. He Has An Appetite And Does Not Seem To Be In Pain. He Does This Mainly In The Evening And Early Morning Hours. He Is 13 Years Old. Any Suggestions Beyond Taking To The Vet? He Had X-rays And Norm.any Ideas

You have excluded pain which is a one of the major cause of heavy breathing in dogs. Other possibility of heavy breathing in dogs is heartworm infestation. Another major reason of heavy breathing in dogs is lack of oxygen which can be due to

1. Heart diseases
2. Lungs diseases
3. Trauma
4. Pneumonia
5. Fluid in lungs
6. Bleeding in lungs
7. Obstruction of air passage

So, take your dog to vet and get his advice after different laboratory and heart tests.