My 2003 Sonata drives, but shakes at low speeds and when stopped (while still in Drive), like it's coughing. If it were a stick, it would feel like it's about to stall. When I place it in Park, it's fine. Any insights for me, so I can tell my Hyundai dealer what the issue seems to be? Last time I brought them an issue like this, they were unable to diagnose. Thanks!