I love the car, 108kmi on it, one owner (doctor) wealthy area, $3800.
Had/has a couple issues. Sunroof gets stuck going back, the common insulation liner in the tracks. Seller thought the AC was not working, but it works just fine. Needs shocks all around, I found a brand new set of OEM installed in a car at my dismantlers yard. Gas tank had a pin hole, looks like he threw his golf clubs in the trunk after a bad day. Once again my dismantler had several, one which was recently replaced, still had it's dealer tag on it.

Best thing I have done to it is change out the rear differential !!!
The older 300S had a bigger diff. just like the 8cyl. cars. Those were 3.69 ratio. For some reason Benz put in the same size diff as the W210's with a 6cyl. into the S320. When they changed the diff. they went to a 3.45 gear ratio which stinks in this 4500lb. car. Even on the highway when the road has a long steady incline you could feel the load BAD. I got a Diff. out of a Sl320 which is the same size in a 3.67 gear ratio, the car feels great now, I think economy actually went up due to the reduced load on the motor.

Good luck with yours, These are great cars!!
I also have a 96 E300 which I turboed.

One more thing, The 16" wheels are horrible. Mine came with the stock common ten holes, and Mich. tires which were like new. The car rolled like a boat in a storm. I wanted to keep the soft ride so I went 17" with 235-55-17. BIG improvement in making the car not feel like I'm driving a waterbed down the block.