engine keeps cutting out

Hi,
I hope someone can help me.
I recently bought an Audi A4 2L. It was working
fine then the check engine sign came on, I was told
it needed a service and thought I would get it done,
however the engine would cut out as I was driving.
There was no warning and all the internal lights
would still be on, just all of a sudden it would cut
out. I wasn't able to restart for another 5 mins. The
cutting out go worse and worse over 3 days until it
would drive a few feet and cut out again. Can
someone please help me try and work out what the
problem could be? Where I could find it and how
much it would cost to fix ? It would be a huge help,
thanks