Head Unit Reboot and Bouncy Voltmeter

On a family roadtrip tonight and on the freeway going 70 and the head unit suddenly goes black and reboots. At the same time the speedo swings from 70 to like 10 and then back up. About a minute later the same thing happened again.

For the next 30 minutes I can see the voltmeter bouncing about every second or two between about 13 to 14 volts.

Any thoughts on possible cause? Battery? Alternator?

Truck is parked with valet so not possible to go pop the hood and poke around right now. Just turned 44k miles today and battery is an Interstate from Costco that is now about 27 months old.

 

My voltmeter began doing same thing (needle jumping rapidly between 13-14 volts). Positive battery cable was the culprit (slightly loose) at battery connection.