(Sorry for my english because i'm Greek

)
So... I have a problem with my car - 1999 passat 1.8T
While i am driving, The rpm moves up and down from 600 to 900 ... when i have the car in stand-by in a traffic light or something like that, it suddenly shuts down!
After that, it is difficult to turn the car on again
i think that it is the Maf sensor... or ISV that cause these problems (all others are checked, fault diagnostic test etc)
Any ideas? Please someone help as I am out of answers and my mechanics cant help me out