Please excuse this post from a newbie, but I've had this problem on my 2015 2.0TDI 150 Jetta.
Symptoms: extended cranking on first start of the day (not necessarily a cold day), additionally sometimes stutters when firing up, and sometimes "farts" immediately after firing up.
Only once created a "pending" P0341 fault code which led me to the "Diagnose Dan VVT valve" video on YouTube and other forums etc.
Was going to throw it back at dealer but checked 12v battery first as thought it may not have grunt to turn over the engine correctly.
Sure enough, battery low on overall charge and only produced 12.2v max after resting overnight. Using a smart charger to replenish battery had no effect. Incidentally, my car has auto stop/start, and the coasting function which increases alternator output.
Bought a new battery (AGM type) and not had the problem in over two weeks.
Original battery was the standard 68Ah Varta which is also found in my Audi A3.
Hope this helps at least some owners to find a fix. Incidentally this issue can be found on Skoda forums too - battery fix was mentioned.
EDIT:
There's an Audi video on Youtube which demonstrates how the VVT mechanism operates in the EA288 1.6 and 2.0 TDI engines.
See here:
https://www.youtube.com/watch?v=M-4xbGeIr58
Think its about 3mins in.