Today my 2006 Jetta TDI starting stalling when I.

Today my 2006 Jetta TDI starting stalling when I was starting off in 1st gear. It happened in the morning but I did not think much of it at the time as I was able to start it back up and drive to work. When I was leaving work, the car would start up fine and remain running. When I put it in first gear and started to take off the car would stall. This happened several times and one of them was a "violent" stall. I had to get home so I just kept trying. Eventually I go tout of first gear and second seemed to give me the same issue but didn't completely stall. After driving for about 20 minutes the issue seemed to correct itself. I say this because I came up on a stop light and when I took off everything was fine. The only thing I noticed was that at certain rpms I had some power issues like it was waiting to "kick in". What could be wrong?