Instrument panel gauge malfunction
 

I have a 96 Grand Am SE. Yesterday while driving home, all gauges on the instrument panel start fluctuating and shortly afterwards, the warning lights ( abs, check engine, oil, battery etc ). A few minutes later, all is normal. Tried it next day and it still happens. No consistent situation as it happens while just turning key to ON position, egine at idle in park, driving on smooth roads or rough. Nothing specific appears to set it off. Battery checked out OK. Any ideas would be appreciated. Thanks in advance