Warning light S in gear wheel

Hello, after my 92er C20NE has now been freshly turned, he has also come up with something to annoy me. The car is an automatic! If the car is cold in the morning, the warning light flashes (not permanent lights) which is A “S” in the gear wheel. If you drive then a kilometer (car slowly warm) or so and then restarts again, it does not come any more and also the rest of the day not. Only the next morning…!!!! Any ideas ??? Greetings, Jörg