Randy it could be a loose connection at the amp guage or a clogged catalytic converter. even one of the temp. sending units could be faulty or a faulty coil all of these could temporarily fix itself after setting for a few minutes. If your car doesn't have an amp guage but has an idiot light then you need to check your ignition wiring the smaller wire coming off the battery or off the starter or at the altenator or where your harness plugs into the key switch all of these will heat up if loose which will cause resistance which causes heat which causes resistance and all this happens really really fast but cools off fairly quickly, just not as fast as it gets hot and causes a temporary loss of a connection.  hope something here helps,  this kind of problem can be quite frustrating