I've had this a few times when the G28 crank shaft sensor fails. Trickey wee thing to replace on the 2.0tdi
But I would advise getting a diagnostic scan done. See what's coming up.
Could be this. First thing to check is that the connector is on it 100%, this is found between the Oil Filter/Cooler housing and the gearbox. It's awkward to get to, but with a torch and a looong screwdriver or suitable prodder, you can push on the connector to ensure it's fully home. If you have to change it, it's a bit of a job (front off/oil cooler housing off at the very least I would say)
If not and to save all the guess work, as B1NCC says, find someone near you with a VCDS/VAG-COM. Good luck.
Stu