A Klasse automatic transmission shifting issues resolved

It certainly could be transmission oil related. I had similar transmission performance issues with my A Klasse. Is the hydraulic fluid level correct? When was the last time you had a transmission flush performed? You need to check the voltage. Undervoltage will cause issues.

Hydraulic fluid level is fine. Transmission flush? Never had one! Undervoltage, eh? How does that mess with the automatic transmission?

Think of it like this: the automatic transmission relies on precise electronic signals for shifting. Low voltage can scramble those signals, leading to erratic shifts. Given the symptoms, especially with the age and mileage, it is advisable to have a qualified technician check the transmission oil condition and perform a full diagnostic. The diagnostic should reveal the root cause and recommend appropriate action. It could just be old transmission oil but could be the transmission itself.

Took your advice and went to a workshop. Turns out there was undervoltage in the vehicle plus the transmission oil was indeed worn. They sorted the voltage issue and did a transmission oil change. Cost 240€ but now it shifts like a dream!