I am not familiar with 3d, so my suggestion may not work. You could use the Area node to create a scanner. Use the "shapeenterd" or "bodyentered" signal to check if the player is in the area. Then, connect the signal with the Timer. When the signal is on, start the timer. Use the "time_out" signal of the timer to trigger the Sprite. I don't know the method you move your sprite, so here is a common way.
self.x += 10