Had the smae thing happen in my jeep. One day I could not shift it out of park without squeezing the button on the shifter as hard as I could, and I was barely able to get it out of park and into gear. I would definately have it checked. I don't feel a click, but I do hear one when I depress the brake pedal before I try to shift from park.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.