Vauxhall Vectra Petrol 1.8 Exclusive 2006. Panel light flashes?

Vauxhall Vectra Petrol 1.8 Exclusive 2006 - my panel light (the one that indicates a light bulb is blown) Symbol; in top middle of dash showing a light-bulb 'flashing.' It lights-up 'intermittantly' and usually at low revs, but sometimes, although more rarely at speed. Ive checked all my lights and all seem fine. When it flashes it does so for a couple of seconds only and then might not flash again for an hour or more. Any suggestions please?