There are many reasons why a cat might leave its nest, and one reason is that if the cat is pregnant, it's very likely to leave to prepare for giving birth. In this situation, the mother cat may seek out a very secluded location to provide a safe environment for her kittens.
If your cat has run away from its nest, you can observe its behavior to see if it shows any signs of labor, such as changes in body shape, decreased appetite, or increased sleep.
