Those reading are well within preferred limits. Since the battery in that is a side post, I would remove the cables and inspect them for terminal corrosion. You might be getting enough intermittent voltage drop for things to act funny.

That would be the first thing to check. Also have the battery load tested. You can take it to any parts store for that. If the battery is original to the car since new, there is a possibility it could be going bad being 4 years old.