I have déjà vu a little too frequently for my taste, and every time I have it I feel as if I've experienced the situation before, but not really. I feel like maybe I had a dream about it before, but it was actually happening when I get the feeling. Except I think that in my dreams, I also think it's déjà vu, except that was the first time...
I guess everyone experienced déjà vu now and then. I think it got something to do with how our brain works which reflects our dreams and reality.