Audi A6 problems change Tiptronic

Hello everyone:
Well, I tell you a topic in case someone can help me, I have an A6 2.5 TDI of 99 with a Tiptronic change and when I turn it in cold He puts the alone and only happens with the car in cold. At the workshop to which I carry it, it does not give any mistake in the machine with which I do not know that it can be. If someone can help me, I appreciate it, thank you and greetings to all.