Re: 2.0 diesel
If you do a search you will find this issue has occurred quite often on these pages. It is undoubtedly the short journeys that cause this problem. Search for DPF or Diesel Particulate Filter, and you will come across causes & solutions.
If you have no choice about doing the short journeys, you should try to give the car a longer faster run as often as possible to help clear the dpf.
This is the kind of thing that is not really covered by warranties, but as you have only recently purchased the car, you might have a chance with the dealership that sold you the car. I wouldn't be too eager to tell them about your consistent short journey usage though. Better to go with the, This must have been a problem when I bought it, attitude.
Good luck, & keep us informed how you get on.