Remove Vehicle. You don't want to discover the significance of antifreeze by being forced to pull over, due to an overheated engine. Antifreeze contains lubricants and anti-corrosion agents to keep components like your radiator properly lubricated and free from corrosion.
Fear, Pain, Excitement. Your dog may shiver due to fright or excitement, an occurrence common in smaller or excitable dog breeds. Some dogs tremble when they encounter other animals, or if they have a form of anxiety in which meeting other people makes them overly anxious. Loud noises ranging from thunderstorms to vacuum cleaners and power tools can also frighten dogs to a point of shivering. Shivering can also be a sign your dog is in pain.
If the dog is wet and shivering, then it's shaking because it's cold and needs to be dried off and warmed up. If it hasn't been running or playing or been wet or cold, then you need to take it to a vet, immediately. It could be any number of diseases or toxins, and you can't help it if you don't know what it is.