Does he have an appetite?
How is his energy level today?
It sounds like she may have a fever which can cause a decreased appetite, listlessness and shaking or panting. You can check this with a thermometer rectally, inserted about an inch, and see what it reads. If it is 103 or higher this is a fever. Normal is 101.0 to 102.5. If she has a fever you will need to see your vet and get some antibiotics to help with this. Fever in pets is usually a result of an infection. Your vet can perform an exam and try to find out what is causing the problem.