A number of possibilities come to mind. Shaking engine suggests a misfire, however, your Engine Computer should detect that and set a diagnostic fault code indicating which cylinder is responsible. That will turn on the Check Engine light too. Even when there's no misfire, a collapsed engine mount can allow a vibrating part to transmit that normal vibration into the passenger compartment. A potential clue is the severity of the vibration will change when you increase engine speed just a little.
Most of the things that can cause what you described are relatively not serious, but can become a bigger problem if they're ignored. Have a mechanic look at it so at least you'll know the cause. He will suggest a course of action, and I can offer a second opinion once I know what is wrong.
Friday, March 6th, 2015 AT 4:15 PM