53 inch rca

 I HAVE A 2003 53 INCH RCA HDTV THE ONLY PROBLEM I HAVE IS WHEN I WATCH SOMETHING THE SCREEN FROM LEFT TO RIGHT LOOKS LIKE IT TRIES TO ADJUDT ITSELF I HAVE SOMETIMES A INCH OF SPACE ON EACH SIDE OF A MOVIE IT STAYS THERE FOR A COUPLE OF SECONDS AND THEN GOES BACK TO NORMAL ANY SUGGESTIONS WHY