I have an R-reg 1998 Volkswagen Golf GTI. For a while now it has been cutting out a few times a week whilst stationary or going at speed, whether the car is hot or cold. Then it won't start for a few minutes, but will always start after this. I have been to loads of garages and lots say that it's a fuel issue, but today, whilst the ignition was on but the engine not running, the rev counter went up a bit and then back down again. Then the car wouldn't start for a few minutes. What's causing this?