shaking/vibration..97 GC 3.0L

When I come to a stop, I feel a lil shaking/vibration, also right before I hit the gas when coming from a stop? Anyone have any clues what can cause this? Other than that feels like a smooth ride when accelerating and coasting..just when about to stop and go...thanks cerivera

Could a bad muffler/catalyic converter do this?
SparkPlugs?
Motor/tranny mount?
transaxle?