Vintage Cars: 380sl transmission, bowden cable, low gears

Question
As I was driving in (D) gear, auto physically stopped but engine kept running. When I put in in (R)-reverse, it did drive backward. When I put gear in low gears (2) and/or (3) it drove forward.
No matter how many times I tried for 10 minutes auto would not move in "D" drive gear.
20 minutes later it seemd OK,,Your opinion PLEASE.

Answer
you failed to tell me the year or mileage
however delayed shift can be due to , low fluid level, too much fluid, vacuum adjustment , band and/or  B2 piston adjustment, bowden cable adjustment, among other things
Was this sudden onset or slow onset?

Could be simply an adjustmetn in the shift lever linkage

Happy Motoring
Ron