Arrgh! 6 speed gearbox cold seizure

[Psilonaught]

ive got a 6 speed FSI petrol and the gearbox just seized up on me in the middle of the road...not good.

The car was out in the cold all evening, and having gone 100m the gearbox froze up. Managed to pull it to the side of the road, and I had to wait until the temp got to 70 before it freed up, worked fine after that

Any idea why this could happen, is it the oil in the gearbox? Car has done 100k, not sure if the gearbox has been fiddled with in previous services

Any ideas, should I take it in to the shop