There could be a number of reasons for your dog shaking. It could be fairly harmless or maybe a sign of something more serious (that could warrant a trip to the vet). Your dog may be shaking due to excitement, anxiety or fear, or he may be shaking because he is cold, or has a fever. If you think he may be cold, bring your dog into a warm environment. If he appears to be shaking as if cold in a warm environment this may be because he has a fever.
A young Brittany lying down on the sand on a beach
Dogs sometimes shake or quiver when they are in pain. A trip to the vet is necessary when you have ruled out shaking due to excitement, anxiousness, fear, or the cold, as there could be a number of medical reasons for shaking.