We had a similar issue with our 2014 Soul. It was the small battery in the Radio/SatNav unit which had failed. The battery wasn't replaceable on it's own and required a complete new unit. Replaced under warranty.
Not 100% sure that's your issue but imagine it could be as similar symptoms. Our Kia dealer diagnosed it by plugging it into a tester so suggest you get the same done, but as you're out of warranty imagine it could be expensive? Maybe try an independent repairer?