The Man Who Haunted Himself (1970)

While driving one evening, Harold Pelham appears possessed and has a car accident. While on the operating table, two heartbeats are even detected on the monitor. Pelham finds his life has been turned upside-down. He learns that he now supports a merger that he once opposed, and that he apparently is having an affair. People claim they have seen him in places that he has never been. Does Pelham have a doppelganger, or is he going insane?