I have a 1990 300SL and a 1993 300CE and these cars start in second gear only when the transmission system is switched in economic.
When the system is switched to standard, it can either start in second or first gear which depends on how far the pedal is getting floored. If I gently push down the pedal, it will start in second. If I push down the pedal abruptly (even when I only push it half), it will start in first gear...
...just some information...
with a minor 600+k