Who or what opened the door to the chest with the saber

Well, the force called Rey to the lightsaber, so I guess it was the force that opened the door...

Well, sometimes you are just chosen. I mean, how did Arthur pull the sword from the stone no one else could do it.
Sure it was locked away but it called to Rey so I would say force.

I think it was just a little visual technique JJ used to create a creepy, unsettling atmosphere, no particular meaning behind it. There are creaky sounds and slightly howling winds/rushes of air added in the background as well (and the screaming child), the lights flicker, Rey looks terrified. The scene was clearly inspired by horror or ghost films. The door sliding open creates a sense of suspense and forces viewers to realize that, while Rey knows she shouldn't be there, something wants her there. The creepiness comes from the mystery. I doubt JJ would be able to give you an answer beyond "the Force?" either.

I agree. It was an effective visual technique inspired by classic thriller/horror movies to build up suspense and enhance the mystery feel. It's actually quite unique when you compare it to the general tone of the movie. It does stand out with this eery, almost creepy atmosphere it creates. There is not really a clear answer as to who or what opened the chest IMO and I don't think we're meant to get one. It's one of those cinematic techniques that's used as a plot device or in this case to create a certain atmosphere/evoke a certain feeling in the audience. This particular shot reminded me of classic fairytales where the hero finds a mysterious box holding some mysterious clue and we as readers/viewers are on the edge of our seats wondering what's inside. I love those types of mystery storylines.

The screaming child was coming from the saber, and the wind I guess because both of those things are in he vision