W204 acceleration problem when the car temperature reaches 90 celsius

[EnnioD]

Hi,
I have a w204 2008 220 diesel with 5G automatic transmission, 155 000 miles. Lately I have noticed a problem with the acceleration.
One day I was stuck in heavy traffic and when I went off, I noticed that the car after switching from 1st to 2nd the rpm arrow went down 2 times in a row even though my foot was in the pedal accelerating.
When the rpm arrow goes down for the second time it gives a vibration. This thing happens only when the car reaches temperature 90, below that everything is okay.
What can be the problem ?
I have changed the transmission oil before 4 months, I also check for the transmission oil level and it was okay.
Please help me

 

[Tonygw]

Is the engine management light on? have you had the fault codes read?
Until you get that done we are guessing.

 

[EnnioD]

I did a whole scan and no fault codes were shown. My mechanic suggested me for a transmission clean up. Is it worth it to clean up because I am afraid if it needs to be replaced and not waste money.

 

[FlorinM]

Since you mentioned that the gearbox had an oil change 4 months ago, I don't think a trans flush would help in this situation.

An option would be to go for a drive with your mechanic looking at live data on scanner, to see if anything is out of range when the fault is manifesting.