Traction control (ESP) coming on when engine cold (1.9 TDI 130)

The other day as I was joining a motorway (engine still cold) the traction control suddenly kicked in for no apparent reason, and what's worse is that it didn't disengage, so I could no longer accelerate. Every time I pressed the accelerator I got the typical stuttering of the ESP suppressing the throttle. Pulled over to the hard shoulder, switched the ignition off and then on and the problem went away and didn't come back for the rest of my 200 mile journey.
The next day, I started the engine from cold and the ESP immediately kicked in, making even the idle super rough. It was stuttering so much I could barely get the revs above 1k. Cycle the ignition and it all went back to normal, followed by another 200 miles without any issues. Since then it's happened on and off, but only when the engine is cold. Any ideas? I don't have VAGCOM or any way to read fault codes.

you need a scan to get the fault code. failing that, start randomly replacing things until the fault goes away. you could start with the injector harness.

Will take it to my mechanic so he can read the codes, and make a diagnosis.