1996 Oldsmobile 88 Strange vibration sound

My car started making a strange rattling noise a few days ago. It is not from the engine as the car runs fine, does not smoke, and the engine temp is fine. I had a complete brake job recently, so I doubt it's loose calipers, also the car brakes well too. I checked the alternator, it is mounted tightly, and the belts are tight as well. The sound is worse when starting, idling, and making slow turns-like entering/leaving a parking space. The car doesn't wobble, so it's not the engine mounting. I was wondering if it might be a bearing in one of the wheels/rotors that the belts are attached to. I have checked under the hood, and cannot tell where the sound is actually coming from, but the closest I can tell, its from the front-to-middle passenger side of the engine compartment.