You feel like you'll lose control for a split second.
Is that because the car suddenly over steers?
It never felt right on the road.
Why didn't it? Poor tracking? Wandering? What? Wandering is due to
incorrect caster angles - from side to side - each side's caster angle
should equal the other.
Have you checked its REAR suspension?
A worn rear bushing, for instance, will allow a bit of rear wheel
steering when its wheel shifts. At higher speeds you'll notice this.
If the tires are not correctly inflated the steering will feel a bit
erratic so don't discount tire pressure.
I own a E320 and have found its steering is quite sensitive to incorrect
toe-in. At slow to moderate speeds the car feels a bit squirmy as the
incorrectly adjusted front wheels encounter small road irregularities
that put additional (or less) pressure on each front wheel causing the
car to make minute course changes. Correct toe-in eliminates it
Dealers often "send out" alignment work so don't accept that "everything
is fine" take the car to an alignment shop and describe the problem to
the guy who will put it on the alignment rack and do the adjustment. And
tell him if it's been in a wreck or not.