02 V6 mustang weirdness

I was driving home from work this morning very carefully, since we just got a snowstorm, when all of a sudden the car starts vibrating. I slowed down, nothing changed. Slowed down more, nothing changed. I took it out of gear, no change. Pumped the clutch a couple times, nothing, still vibrating. Revved the engine a couple times, no effect up or down. I turned into my driveway(its a short trip), came to a complete stop, still vibrating. Doublechecked the gear-shift, re-clutched, and revved the engine once more, then finished the trip up the driveway. Slowly, the vibration stopped. Happy to have made it home, i went to bed.
This afternoon I peeked at the U-joint, and from a cursory exam it looked ok. I drove it to the store with no problems.

The vibration was a lot like you would feel if you were to come almost to a stop with the car still in gear, but like i said, the rpms/gears/clutch position seemed to have no bearing on the vibration.

So im stumped. Anyone have any ideas what might have been going on and if its something i should worry about?

Could it be the ABS effect? , because of water, Ice, or snow!

Could be ABS but OP states it was still vibrating at a complete stop. Was it vibrating from the engine? It might have been water getting in a COP. That is of course if the V-6's have COPs like the 4.6L's. Assuming the do, remove the COPs, inspect the rubber boots for any holes and replace the boots as necessary. When re-installing, apply a generous amount of dielectric grease to the boots to seal out moisture.

i know this is an old thread but as someone who drives his mustang all year long with severe winters if youre not used to the snow and ice you could have had anything freeze. from suspension to brakes or even a piece of ice stuck in the brakes makes a hell of a racket. snow packed in the wheel wells the list goes on. i know once a year and only once a year during the winter my air flow controller gets frozen....which is a real pain when its 20 below zero and youre trying to take it off to clean it....after one cleaning its fine for the rest of the year....sigh...i luv my car.