RepairPal Certified shops can diagnose and repair your 2005 Volkswagen Jetta. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
This is a complex car with the turbo diesel. You really need a scan tool to see what is going on, it could be defective engine sensor, etc. Too many things to just guess about.
here are some shops:
https://repairpal.com/volkswagen-repair-in-carrollton-texas