My previous 1981 300TD one day (after a regular service) decided when cold to accelerate to maximun r.p.m. in first gear, stay there for a few seconds and then it would jump into second (braking your neck at the same time).
The problem would solve by itself once the engine heated up a little.
The M.B. dealer, in charge of the regular service, took back the car and kept it for three days trying to figure out what the problem could be.
They found out that the mechanic who performed the oil filter change have switched two hoses of the vacuum system that commands the gear changes on the auto transmission.
Maybe that day you had an intermitent problem with the vacuum system. Who knows? Although, I am not sure if the W124s autos work with vacuum as the W123s autos did.
Just a thought.