Just bought a 1990 300SEL 94K miles. I find it shifts fairly smoothly from third to fourth but harder from second to third. It is normal for the shift quality to differ depending on the gears involved? If not, what would be the cause?

The vacuum modulator is not leaking. The linkage in the engine compartment has been adjusted. The trans fluid and filter have been replaced in the past several thousand miles.

I haven't tried doing a first gear takeoff so I don't know what that shift is like. I'm not really concerned about that at the moment.