What causes lip shaking..my upper lip muscles is shaking voluntarily?im getting anxious with it.what would it be

Anxiety Itself: Do you mean "voluntarily" to mean "on its own" or by your purposeful movement? At your age, the most likely cause of a lip "shaking" would be anxiety, which is a sense of ill-at-ease which has no specific focus and is biologically determined. If you then are nervous about the lip movement, it likely will shake even more. I encourage you to seek anxiety management: relaxation, therapy, meds, etc.