My 1999 VW Beetle Diesel sometimes won’t start (especially when hot) and sometimes the engine cuts out while driving and may or may not re-start. I have it to the mechanic for several years and they have done a lot of work but is is getting worse.
You need a new mechanic, preferrably a VW specialist and someone who understands diesels.
they have done a lot of work but is is getting worse.
We might be able to provide some specific ideas, if we knew what has already been done. Beyond that mcparadise’s recommendation is about all we can offer.
You might want to post your question at tdiclub.com They are the diesel VW experts.