Your batteries are ten years old, they are trying to say goodbye lol.

If you don't drive it for extended periods of time you might have to put a charger on it occasionally. A short drive will often not let the alt do its job long enough to put back in what you took out by starting it. In addition as batteries get older they will lose more voltage at rest than when they were new. Your batteries have a few more years left if you just keep doing what you are doing,