The reasons why the dog’s legs keep shaking:

1. When the ambient temperature is below 10 degrees Celsius and it is extremely cold, the dog will tremble.

2. When dogs are nervous and fearful, they will tremble.

3. If a dog’s leg is injured, such as trauma, fracture, etc., the dog will tremble due to pain.

4. When a dog’s body is severely deficient in calcium, it will also cause the dog’s legs to keep shaking.

Solutions to the dog’s legs that keep shaking:

1. If it is caused by cold, measures should be taken to keep the dog warm to prevent it from catching cold cold.

2. If it is caused by stress, the owner can calm the dog's mood and wait for the dog to recover on its own.

3. If it is caused by injury, the injured part of the dog should be treated to relieve the dog’s pain.

4. If it is caused by calcium deficiency, the dog should be given calcium supplements in time, and the dog should be exposed to more sun to promote calcium absorption.