I have the same hard shifts from first to second in my 1992 300TE 4matic when it's cold. All other shifts up and down are smooth too. I also bought my car used, and both the previous owner & dealer told me it was "normal". When I can, I try to drive it as far as I can in first gear to warm it up a bit and have found a 1/4 mile is often far enough to get a smoother upshift.