The Kawasaki Ninja 125 cc can be a suitable choice as a starter bike for a first-time rider. It is designed with beginners in mind and offers a manageable power output that allows you to develop your riding skills gradually. The Ninja 125 provides a comfortable riding position and nimble handling, which can be beneficial for new riders.
Considering your height and weight, being 5'4" and 45 kg, the Ninja 125 should be suitable for you. Its compact size and lightweight nature make it easier to handle, especially for riders with a smaller stature. However, it's always recommended to visit a dealership or sit on the bike in person to ensure you feel comfortable and have a proper reach to the controls.
Additionally, as a new rider, it's essential to take a motorcycle safety course and wear proper safety gear, including a helmet, gloves, and protective clothing. These measures will help ensure your safety and enhance your overall riding experience.
Remember to check the licensing requirements in your specific region or country, as they can vary, and consult with local authorities or riding instructors for personalized advice based on your circumstances.