If you're after a car with a forgiving ride then the previous Mercedes-Benz C-Class may be worth considering. Avoid the Sport models (as these have stiffer suspension) and look for Avantgarde or Elegance models. Most of these are automatics (especially the C180K or C220 CDI versions) but the key thing is to find out what size wheels it has. Standard wheels on these are fine, but there are larger wheels available (as an optional extra when the car was new) and these can have a detrimental effect on the ride comfort. Also make sure that what you're looking at is the four-door saloon and not the three-door 'Coupe' model which are sportier and not as comfortable.

Another car to consider is a Volvo, as these have a smooth ride and the most comfortable seats of any manufacturer. Again, avoid any Sport models (go for an SE) and you'll find that most are automatics with the Volvo 'geartronic' gearbox.