After driving for 35 minutes then turning the wheel in the parking lot. It because hard to turn right. My power steering fluid is at the right level. Belt been changed also. This is for 2011 mercede e350 rwd
Double check your fluid level. Mine used to do that too, but it was a little bit low. Added a little fluid and it all went away. Racks also go bad, but it's very rare. Also I've changed the belt, tensioner and the two idler pulleys, they're also well known to go. There's usually some play in all three of those.
I've had racks go bad in two cars I've owned over the last 10-15 years. Both presented the same symptom-- random "tightness" or resistance to turning that came on suddenly. It was not repeatable; if you let up on the steering (or bumped the wheel the other way) then pushed in the desired direction once again, it would usually cooperate.. I can't recall if it was problematic turning only one direction, but it made for interesting driving when your steering wheel freezes up in the middle of a turn!
Does your Mercedes require a special fluid, and if so, has that fluid been used religiously with no top-up of regular fluid? That's how the rack in my VW got torched, I used regular Autozone power steering fluid for top-up instead of the uber-expensive synthetic German fluorescent green Pentosin stuff I was supposed to use. Turned all the fluid into a tan milkshake color and trashed the rack. After a flush I was still able to drive it but the problem never went away until I replaced the rack.
Power steering (pentosin)fluid was changed along with reservoir, power steering cap, and changed the belt, tensioner and the two idler pulleys all of them last year. The only issues I have is both of the wheels bearings is going out on the front end , also has crack wheel on right front side that causing loose air while driving down the road so I have to fill it up before it get to low.