I am a 20-year-old girl, and occasionally I want to solve my physiological needs with my hands. Is this normal?

This situation is normal. Everyone has desires, whether boys or girls, especially girls your age. It's normal to have physical needs. It is a good way to release stress to stretch your body and mind with your hands occasionally. You can also borrow some equipment, which will be more comfortable, but you must not indulge in this happiness.