Sometimes your balls jiggle by themselves why do they do this?

The jiggling of the testicles, often referred to as "testicular movement," occurs due to the contraction of the cremaster muscle, which is responsible for raising and lowering the testes to regulate temperature. This movement can be triggered by various factors, including changes in temperature, physical activity, or even arousal. It's a normal physiological response and helps maintain optimal conditions for sperm production. If you experience unusual discomfort or changes, it's best to consult a healthcare professional.