I have had my C-max for nearly a year and for the first, few weeks experienced the same problem, just as Kevmond says. I learnt to give it a little more welly when pulling away slowly into traffic, at roundabouts for instance, before letting in the clutch. The car seems to require more revs than I was used to applying on my previous Tino. I have now got used to it and it has been a while since I last stalled, but I do lapse occasionally.
Richard G, might well be right and the underlying cause may be the accelerator pedal resister. However, applying just a little more power has solved the problem for me. It could also be that, with the lower powered engine and the same weight of car, you might require to apply even more revs.
The reason that it is only happening now could be that you are now driving a little more gently than you used to. (trying not to burn too much fuel?)