‘Shivering’ can be a sign of many different problems. Some dogs, especially older ones, can develop muscle weakness that can lead to shivering. It can happen to others that have underlying pain, discomfort or even neurologic disease.  More commonly, shivering can be a sign of anxiety or fear.

I recommend that your veterinarian examine him, as it is important to rule-out causes of pain and disease. Also, be aware of what is going on in the house when he starts to shiver. This may give you a clue as to what triggers it. If he only does it when he is alone or after a sharp noise, it may simply be fear/anxiety. Talk to your veterinarian about what specifically can be done to help him in these situations. Sometimes he may just need a little reassurance, but often specific behavioral modification or training can help tremendously in helping him gain confidence.