I am with Mike on this one, and Terry on the pause at anchor. If I do not have my bow arm fully extended, I shake. When I do this, I usually hit left by several inches.
As soon as I extend my bow arm fully, and draw with my shoulders, I pause briefly at full anchor and no shakes. One way I figured out I was shaking was to count one-one thousand, two-one thousand at anchor. That slight delay in the release gave me time to realize I was shaking right before the shot.
One useful technique may be to steal a page from the PSE wheely coaches. Try standing or sitting in front of a target at close range. Draw with your eyes closed and "feel" your form. Practice shooting several arrows with your eyes closed, focusing only on form (push-pull, anchor, breathing, etc.). It can really help you with proper form by eliminating the focus on aiming,freeing your mind to focus purely on form. Any time I feel I am really struggling with form, I use this exercise to re-enforce proper form and muscle memory of what a solid draw should feel like. It really helps me with accuracy. Shooting with your eyes closed can take some getting used to. You may have some one watch you to see if you flinch or pull your head away from the bow when you shoot. In other words, after the shot, be sure to follow through.