I've read that sometimes your subconscious picks up little things you don't register and puts them together to make a scene that you put in the back of your mind. When something happens and your brain has put together a scene that matches it, you experience Deja Vu.
After watching a Wizards episode, I was convinced (for quite a while) that we have Deja Vu because a wizard has turned back time. Don't laugh. Almost every die-hard fan thought the same thing.
Somebody told me that if something happens that happened to you in your past life, you experience Deja Vu. I'm not sure I believe in past lives and stuff but the explanation certainly makes sense. If souls have multiple lives.
Anyways,
Adios.
