ANSWER – Before shaking the tree, if the player makes it clear that should the ball drop and be identified, then they will take an unplayable ball relief for the ball having been unplayable in the tree, then there is no penalty for causing the ball to move. The player may then take relief under Rule 19 using the point on the ground vertically under where the ball was as the reference point.
Should the player not make it clear of this intention, then they would incur an extra 1 stroke penalty for having made their ball move.