Car shimmying

I have a 2001 Mitsubishi Galant 4 door sedan automatic. Yesterday, the car started shimmying and the service engine soon light came on. I don't feel the vibration thru the brake itself, but more like the entire car. It is much more pronounced when the car is stopped but still in drive than when the car is just in Park.

This occurred when my husband was driving so when he described said it "felt like the engine was bouncing around, " my first thought was motor mount. But after driving it myself around the neighborhood and seeing the difference when the transmission is engaged, I'm not so sure.

Any suggestions would be greatly appreciated. We're broke, and this is our only car. No public transportation options where we live.

Many thanks.