Five or six times now in the week I have owned my 1994 530i, the horn has begun to blast without apparent reason. It always occurs within minutes of starting the car, not always from "cold". Each time, the vehicle was stopped, the doors opened,locked with the key, then reopened and this cured the problem for the rest of the trip except for today. My wife went throught the routine but had to repeat it a second time when the horny little devil started again within metres of the restart. Any ideas? This really is a nuisance and I have no idea what is going on.