my 150,00mile 1989 90 with a 2.5td (not tdi) does the same thing. fills the street with blue smoke, which dies away after about 5 minutes, so I too would like to know!!!
a neighbour reckoned it might be the valve stem oil seals that are duff, so they let oil into the cylinders the engine is stopped, and the oil burns off when it is started.
Not sure if it is though as he is a legendary bullsh***er
I had assumed it was just a standard feature of a 17 yr old landrover.