I have a 2011 S550 (previously flood damaged) with a strange steering problem

when I drive along, steering wheel center starts precisely in position, then after a right turn or two, its center is about 15 degrees clockwise, so I drive along a straight and instead of its sitting level at 9 o clock and 3 o clock, its moved to just before 10 o clock and just before 4 o clock.

Then after a few left turns it drifts back to center. Position perfect again.

There is no play in the wheel as such so its something affecting the steering itself

I would appreciate any pointers as to what to check first, is this something a garage could locate easily?

thanks