It's baaaack! HELP

I would start with your battery post connections to make sure they are clean and tight, then I would move to the firewall bulkhead and unplug, clean, ad any type of anti corrosion product and plug them back in. If you still have the problem the next step would be to pull the gauge cluster and make sure the voltmeter gauge wires are clean and tight. Lastly would be the ignition switch, since it is a M_ _ _ er F _ _ _ er to service you might want to get some sprays for electronic components that you can try first. Good Luck