I can't be the only one with this problem.
When my 300SE (126) stands in the sun for a while the roof get really hot. I am rather big (just had to weld my seat after stretching in a traffic jam), and sit with my head (bald) very close to the roof. The combination of the cold air from the airco and the heat from the roof makes me feel like frozen steak under the grill. Today I took off the lining and put some heat insulating foil between the lining and the roof. This really helps!