That is most definitely not the phone but an app you've installed (unless you're using an ad-subsidized phone from Amazon, but even those are going away). Check the notification or the screen that shows when charged (the notification you should be able to long-press it to get info from the app that's causing it). It's usually File Managers or RAM Optimizers or App Cleaners that include these obnoxious 'features', and in most you can disable them from inside their app settings, but still, I suggest you just get rid of the culprit app.