Re Twilight Zone. Hi, I am trying to find out the name of an episode I saw many years ago. It was about, time & space is only created when you walk into the next room, it showed a guy in a room but there was just blackness.

I think you may be talking about the ep. "Little Girl Lost." link

Perhaps you are thinking of "A Matter of Minutes" from 1985?

I remember that episode because Adolph Caesar who starred in "A Soldiers Story" was in it. The idea was that a guy gets unstuck from time and goes backstage to witness the construction of a new instant of time. link