Hi lads

Have got some problem don't know is it serious but maybe someone had this or currently someone has it so would be great to hear from u some advice or even problem solution.

Here's the problem:
When starting the car in the morning or whenever the car is cold, starting well RPM is 0.9 but in a 30 seconds RPM suddenly drops down to 0.6 and u can feel some vibration, when engine got his 90 degrees i have to turn off the engine and start again, then its stays 0.9 RPM as normal. I just don't have a clue why this happens.
One mechanic said i have to change the lifters as they re gone, but engine sounds very well no any foreign noise.
Could be MAF throttle body, EGR valve, maybe coolant temperature sensor so no clue where to start.

Was doing some research in the net but didn't find many information about 2.5tdi's

Thanks for reading