The simplest answer for, "Why is my dog shaking?" is that they're cold. Shivering in frigid environments is an involuntary response designed to get the blood pumping in order to raise body temperature and prevent hypothermia. Smaller dogs, such as Chihuahuas, may be more prone to shivering than larger breeds due to their lack of body mass and insulation, explains Wag!.

What you should do: If your dog doesn't fare well in the cold, consider limiting their exposure. A dog sweater or coat can also help them stay warm and ease shivers. Also, give them a warm place to curl up; a dog bed near a heating vent with a warm blanket can do just the trick on a cold night.

Some dogs shiver when they're happy or excited. No one is sure why, but one theory is that it's an outward manifestation of intense emotion. There's no danger in this type of shivering; it will most likely stop once they calm down.

Other intense emotions that can cause shivers are fear and anxiety. While shivering, in this case, isn't harmful in and of itself, stress isn't any better for your dog than it is for you.

What you should do: Do your best to reassure your dog and, if possible, remove the source of the stress. If your dog is prone to shaking during thunderstorms, for example, try to help them stay calm by introducing therapeutic toys or masking the sounds of thunder. In general, if you notice something consistently turns your pup into a shaking state, try to redirect their attention. Dogs are also very perceptive and if you are stressed, anxious or afraid, they are very good at mimicking your emotions. In certain situations, when you remain calm and ignore a stressor in your house, your dog can pick up on it and learn that it's nothing to be anxious about.

However, if you rush to comfort your dog every time they're shaking, they may learn that shivering is a good way to get your attention. Some dogs even turn on the shakes while begging for food to earn sympathy.

Shivering could be a sign that your dog is in pain or suffering from an illness. Shivering and muscle tremors can be symptoms of serious conditions such as distemper, hypoglycemia, Addison's disease and inflammatory brain disease, as well as more common ailments like an upset stomach.

Constant shivering could be a sign of generalized tremor syndrome, also referred to as shaker syndrome, a chronic condition that can be helped with medication, according to Wag!.

What you should do: Look for other signs of sickness or injury. If the shivering is accompanied by abnormal behavior or seems out of character for your dog, contact your veterinarian immediately.

It's not uncommon for weakening leg muscles to develop tremors as dogs age, but shivering could also be a sign of arthritis or joint pain.

What you should do: If you notice your aging doggy starting to shake, it's best to get them checked out by the vet.

Normal shivering and shaking are much different than a seizure, during which the muscles seize up and a dog loses both mobility and awareness of their surroundings. If you suspect your pup is having a seizure, and they're not already being treated for a seizure disorder, get them to the emergency vet ASAP.

While most causes of shivering in dogs are relatively harmless, it's best to reach out to your vet if you're wondering, "Why is my dog shaking?" They can explain what causes a dog to shiver as well as uncover if something serious may be going on. Even if there isn't cause for concern, you'll have peace of mind once you get a vet's assessment.