Vauxhall Vectra speedo, rev counter, fuel and temperature gauge stopper working

the speedo, rev counter, fuel an temperature gauges all dropped to zero although the engine still ran and I drove to work. After stopping and showing them at work, put the key back in the ignition and all the instruments wokred again. Went to go home tonight and dash instruments now not working again - is this a common fault - any ideas what it is. Contacted loca garage as car still under warranty they say this sometimes happens and to disconnect battery for 10 mins then shouold be fine - is ths right?