By coolbeanwalker from west Sussex, north Yorkshire
My daughter has a Boxer that shivers, and she puts one of her husbands old sweaters on him. She puts his two front legs in the arms of the sweater and puts his head through the neck opening.
Small dog? Cut sleeve of sweatshirt long enough to cover his butt. 2 holes for front legs, angle cut so plumbing parts can be used. Medium dog? Use leg of sweats long as it has a cuff. I like these better than jackets bought as they cover the behind parts.
Dogs and even cats can shiver no matter what the weather, first I would check to see if they have a fever, then if they do take them to a vet. Some dogs and cats will shiver do to being nervous as well or afraid of something. If its cold out then put a pet sweater or jacket on them and pants for dogs and cats too.
He/she might be sick take the boxer to the vet