Hey, i shoot instinctively as well. I got an old compound bow for my first with very little let off(maybe 20%) and the draw is around 63. sights made me shoot worse, so i took them off and shot. The first couple shots were great, but, like you, i had the same problem. A couple things that are good to change is, after a few shots, you start paying less attention to what you are doing and start focusing more on strength to pull the bow back. Be sure to watch how you are releasing(if you shoot fingers) or make sure you dont jerk the trigger(if you shoot with a release). Also, you might just want to practice more and build those muscles it takes to stabilize a bow. They arent muscles you use everyday, so naturally, they wont be as strong as others. Take Care and let me know if you have any more questions.
Mark