Although I normally recommend against changing parts without some diagnostic inspection, this is most likely the crankshaft sensor failing.
Buy a proper Vauxhall sensor, cheap rubbish off ebay will cause more problems than it solves.
Any garage can fit it, doesn't have to be a Vauxhall dealer. The job only takes 20 minutes but many garages have a minimum charge of 1 hour labour.
It's a fairly easy job to DIY, get the Haynes manual if you're unsure and want to have a go.
biggy, July 2009
