It's battery related. You can jump up and drive to autozone to

Autozone provides free test. If battery is non-chargeable, you can buy a new battery for maybe 50d, they can help you put it on if you ask.

If you know your battery has been more than 5 years or 60kmi, go get a new battery so no worry for next 5 years.

The reason this is happening is because (1) maybe your car leaks power somewhat; (2) May be your battery is aged it won't hold much more and longer; (3) hot weather kills battery, now it's summery...