Never herd that before..Does the battery have sufficient charge, are the terminals clean and tight, are the connections in the auxiliary positive supply box clean and tight and is the box secure on the positive clamp??? Main engine earth between the chassis rail and starter motor can corrode and internally break as can the terminals corrode. Try to see if a good jump lead between an engine bolt and a bare chassis point makes a better earth.
Could be a fuel issue in that the injector loom is not telling the injectors to open, tandem not supplying enough fuel or too much air, clogged or water in the fuel filter even lack of fuel in the tank.
Has any work been done on the car? Does it fire for a second or two then die - immobiliser issue?
A VCDS scan COULD tell what the issue is if it logs a fault in the cars modules.