Why is your rat terrier acting scared all of the sudden?

Your rat terrier may be acting scared due to a variety of reasons, such as changes in their environment, loud noises, or unfamiliar people or animals. Sudden fear can also stem from a negative experience, like a traumatic event or illness. It's important to observe any changes in their behavior or surroundings that might be contributing to their anxiety. Providing comfort and a safe space can help them feel more secure.