Maine-MB

I have a 2005 S500 4matic. After the car is warm it shudders/vibrates when making a slow turn, such as when parallel parking. When the car is cold it doesn't do it. Anyone have any thoughts?

The front CVs are good and I replaced the rear drive shaft assembly about 10,000 miles ago. Neither of those should be temperature related anyway.

S_Holford

Combination of low power steering fluid and bad motor mounts? Worn out belt tensioner allowing the belt to slip? Just some easy things to check first.
I don't know how these cars act when the rack & pinion begin to fail but hopefully it's not that.

Maine-MB

The car has to be moving for the problem to occur. I thought about the power steering pump or maybe rack but they don't really fit with the circumstances.

S_Holford

Are you feeling the shudder in the steering wheel and vibration throughout the car? If you think about what's going on, low engine speed during turning/parking, then additional load of the power steering demand when turning at low speed. It has the symptoms of low fluid, low pressure, slipping belt/bad tensioner if I'm interpreting what you're telling correctly. How old is the power steering fluid? I'm still leaning towards motor mounts for the vibration. They're hydraulic and once they've failed, you'll feel everything the engine transmits to the body. Are you getting any power steering groaning,cold or warm? These are just things I'd do first to troubleshoot it and some first steps you can run with. I don't know what your level of mechanical aptitude is so don't be offended if I'm sounding very elementary about it.

I'm not familiar with the 4matic components so maybe someone else can chime in there if they think it could be related. Good luck.