Vw jetta 2.0 tdi frustrating intermittent starting

Hi everyone, I have been a long time lurker and used this site to resolve issues on my VW’s in the past but this issue I now have is a bit more vague:

I have Vw 2.0 Tdi Jetta sport 2010, and has an annoying issue of not starting some times. Basically go out to car and starts first time depress clutch apply small accelerator andd car starts fine. But some times after a trip/ drive it will not start got to start it and it peters out with no real cranking after turning the key, plus the rev counter barely rises at all. It is annoying because it does not do this all the time. I have been temporarily stuck at petrol stations and car parks but concerned if I stall it at junctions etc. Jetta has 72000 miles, cam belt and water pump was replaced at correct intervals . Drives smooth and fine on rest of time. No smoke and no vibrations. Looking around the forum could it possibly be a cam position sensor. I am very much a novice with these things and hope a more knowledgeable person can advise before I take it to a Vw garage .
Kind regards and thank you in advance!

We don't see many Jetta 5's but we have a 2L FSI in today for brakes. You don't need to give them any gas on starting, the ECU will ignore whatever you do. My assumption would be crank speed sender G28 rather than the cam sensor G40 due to the rev counter reading and these often do not generate a fault code. They are a complete PITA to replace and if the screw head rounds out that is box out, clutch/flywheel off, sump off, new rear main seal and a special jig to install it. You need a top quality sharp new very long ball ended M4 hex key.