It does not happen all the time, but when I drive my 1995 Lexus LS400 on a highway for a long period of time (at least 1 hr or more) at high speed when I slow down (exiting from the freeway); the RPM goes to ZERO and the engine shutoff. I put the transition on NEUTRAL and turn off and turn on again. The engine is fine and I can go for a long time.

Do you have any ideas what? I have taken it to the mechanic and they could not find anything wrong with it.

Thanks,
Carlos