S3 indicator on dash blinks and car won't start

Every so often, the s3 indicator on the dash will blink and the car will not start. I have to spend 5 to 10 min. Moving the key from off to on to get the blinking to stop. When the indicator is not blinking then I can start the car. Any ideas? I think it might be something in the steering column where the key goes into but not sure. It's a 1991 model.
Thanks in advance!

Ez