This is something that bother me also. When a Sprite's movement is based upon the mouse position, when the layout begins the Sprite begins to move without the user doing anything, just because the default mouse position is where ever the mouse is on the desktop at the time of the game's initialization.
Ideally, the mouse object should be inert until the user does something or the game tells it to do something, and the initial position should be fixed (if so desired).
Check the attached capx to see what I mean. Is there a workaround that?