yeah, you want to release around shoulder height..
It might be that you are rushing through the motion too quickly. I tend to have jerkness in my tossing arm, and try to fix it for so long.. And my coach kept telling me to slow my tossing arm down. No matter what I did, I couldn't do it...One day after watching him serving, I realized that I had to concentrate on slowing down my ENTIRE body.
My problem was that my right arm was moving fast, and I was trying to slow my left arm down -IMPOSSIBLE THING TO DO.
So why don't you try to slow your entire motion down until you get into launch position, then explode into the ball.
Another tip- try to keep your tossing up arm up as long as possible this will prevent you from THROWING the ball up, rather than placing the ball in the air.