Idle Speed Increases When Starting Engine

Good evening.
I've been having a problem with my Audi A4 (AFN) 1.9 TDI since just now.
'When I start my diesel engine, the RPMs automatically increase to around 2000 RPM, then go down, and then increase again. After that, the engine shakes, the RPMs return to normal, and stay there. It might be my imagination, but I think there's also a loss of power.'

Does anyone have any advice from afar?

Regards:
Rainer.

Edit:

I just found this thread.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

I'll check tomorrow morning to see if the engine speed is correct again.
It might also be due to a faulty temperature sensor in my case.

And another edit:
Everything is okay again.
I will observe that! Therefore, the temperature sensor is a possible cause.
Thanks for reading.

"I had the exact same problem with my 1.9 TDI ASZ 130hp engine. When starting, whether the engine was warm or cold, the RPM would sporadically and non-reproducibly jump to 2000 rpm, as if someone was pressing the gas pedal. In my case, the coolant temperature sensor was still the original one. I replaced it. It hasn't happened since, and that was two months ago. Let's see how it goes..."

Good evening again.
Today I went to the mechanic, and they read the error codes. The code that appeared was for the alternator.
About two months ago, my car battery died, but it had been defective for a longer period. It was no longer able to charge. This probably caused the error message regarding the alternator.

I also strongly lean towards the sensor option.


Regards:
Rainer.

Edit: So, about half an hour later, after I had driven the car 22 kilometers and parked it, it started up normally again. A temperature sensor that is displaying incorrect values could really be the cause in this case. I will definitely replace it.

Update: Just ordered it... I might install it tomorrow.

Okay, so the sensor has been replaced (Hella brand, €19.95), and everything seems to be working fine so far.
I'll post again in this thread in a few days!
Thank you for reading.

Regards:
Rainer.

Okay, a few days have passed and everything is fine so far.