Horn Honks for no Reason

Has anyone ever heard of this one, I have a 03 Malibu and the horn honks sometimes for no reason, it always honks when I start it and yesterday it decided to honk while I was behind someone while waiting for a train, I have no alarm system on this car.
any ideas what may be causing this?
Steve

Most likely the horn pad or a wire intermittently getting shorted out.