Children have different levels of tolerance. While some can handle lots of sound and ovement all at once, others find that overwhelming. It sounds like your baby is telling you that this mobile is more than he can handle. Try just letting him look at it without turning on the music. When he seems to be calm and enjoying that, try gently moving it so he can see it turn. If he likes it, you can try adding the music. Slowly and sensitively introducing him to more stimulation can help him build greater tolerance over time