I think you need to determine how your transmission was designed to operate. Your owner's manual should tell you. Not all automatics coupled to the 617 shift the same way. The 77 300d I owned always started in 2nd gear unless you took steps to get it into 1st. You could either engage the kickdown switch or while at a stop, put the lever in L then back in D. It would then start in 1st gear. This was explained in the manual.
The 79 300sd I have will automatically start in 1st gear but only if the car comes to a FULL stop first. If the sensor does not feel the car come to a complete stop, the transmission won't shift down to 1st and will start in second unless the kickdown switch is engaged.
The 85 300TD always starts in 1st gear.
Simply counting the shifts will tell you what gear it starts in.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13