Rich,
this could be a loose connection. Does it happen more on bumpy roads and rides or all the time? If you have a volt-ohm meter, and can get to the leads going to your volt meter, connect them to the volt-ohm meter and go for a drive and see if it bunces around. If not, then check the gauge and the connectors to it. I put spade connectors on all of mine for this purpose. Just takes a minute to disconnect the in dash gauge and connect it to one in the seat and I can then determine which way to look. And never forget the famous loose ground connection.
Ron
