1998 320 78k. The engine vibrates / shakes when started. Turn off the ignition and restart vibration stops. Looking for a starting spot to diagnose the problem. The vibration occurrs maybe once per week. No CEL. Thanks
You really need to get your codes read. AutoZone will do it for free. Get the codes and then post the actual codes here [not the counterman's interpretation] and we can try to give you a hand.
One recommendation I will make is to get the almost universally recommended #94169 Cen-Tech OBDII reader from Harbor Freight. Mine has already paid for itself many, many times over.
From the way it is written, your description, unfortunately, could be many things... get the codes.