[SCRIPT] How do I make a chair move?

[FlawlessHappiness]

Everyone here gave some pretty good examples, although some of them are a bit complicated.
I'm not sure how experienced you are with scripting.

You didn't specify how often and for what purpose the chair is moving.

To me, it sounds like you just want to create a little scare where the chair does a quick push towards the player.
If this is the case, I would go with CJ's solutions:
Have a simple script area. When the player collides with it, use AddPropForce to push the chair a bit in a specific direction.

You said the hallway was narrow, so whether the chair is pushed directly towards the player, or just in his general direciton shouldn't mean much.
As long as the chair moves, it'll appear spooky.