I've had this happen, if the idle is correct and if the shit from 1-2 or 2-3 is hard then the trans shift solenoid is sticking and will probably need replacing for around $250. The bad motor mount will also transfer all of the engine vibration/shock to the body and is easily checked with a screwdriver or small prybar, try to move the engine side of the mount from front to back while watching the rubber mount material. It should be solid and not separate. A mount is under $30 and can be replaced by the average person with caution. Good luck!