What does it mean when your dog shivers but all of his normal activities are fine?

There could be several reasons. An underlying condition could cause the shivering, such as an injury, genetic trait, or disease. Some dogs shiver when they are feeling off. It could just be temporary, such as a troubled digestive tract or a mild cough. Some dogs shiver when they are tired, lonely, excited, bored, or in some other emotional state. If the dog's shivering persists for more than 48 hours you should take it to a veterinarian.

Another answer

When a dog shivers, it's usually because they are anxious, excited, nervous, cold or in pain. If you are worried, I would have a vet check your dog out, to make sure there is no underlying medical problem.

Another answer

If your dog is a chihuahua or a tiny toy poodle they, it would probably be normal because they are so small, but it also could mean he is in pain. I have a chihuahua and it was shaking and it has never shook before so we took him to the vet and he said he had a pinched nerve in his back! all the vet had to do was give him a quick shot and told us to give him some meds for the pain. we put the pill the vet gave us in chicken or meat [something he likes] and he was better in about a month so i think you should take him to the vet just to be safe.