MIL warning light turns on intermittently, and there is a vibration?

It stays on for a few seconds (19-20). At the same time there is a vibration in the car as if something was loose. Two days ago it came on four time on a trip that lasted about 40 minutes. Each time was different although the last was the longest with much stronger vibration. Yet on the way home, about 2 hours later, it never came on.

Hyundai service mechanic checked it out but could not find anything wrong. That didn't surprise me because it is an "intermittent". However the next day the same thing happened one time in a journey of about 2 miles then didn't happen with a follow-up trip of about 20 miles.

Thanks