Here is a concept of very simple robot toy. Two CD were used to make its wheels. One IR proximity sensor detects the presence of your hand and switch ON the motor. The circuit was explaine in another video
https://www.youtube.com/watch?v=soa13KhVzsE
Repetitive placement of hand in front of it gives enough momentum to have a complete rotation. During that full rotation the floor reflect the IR and the sensor, switch ON the motor again. Thus the toy gets more momentum and move forward with random motion.
آی-ویدئو