What is the best method to move object(Ex-Cube)when the player is close to that object?

currently, I'm developing a VR based game for stressed people for my final year project. I want to make a scene like when a player is getting closer to an object(Ex Cube), that object should move to another place, and again that person is getting closer to that moved object, it should move again to another place. Likewise continuously I want to create a scene like that. What is the best method to create that?