For the past few days, Caesar has been shivering for no apparent reason. Shivering like a chihuahua. It's really weird. I'm sitting here in my warm cozy house, and he's curled up on my lap.... shivering. Just his whole body is shaking like he's cold. It's not like he's nervous or something, because he's resting right now. I noticed it on Thursday and didn't really think anything of it, and then Friday the dogs went to the kennel (because my brother got married this weekend), and then we picked them up today and it seems worse, it's more constant. Nothing else is different.. he's eating, drinking, playful. What could this mean and how soon should I get him into the vet??