This happens whenever my battery gets to 20% or lower so people avoid using to the point of saver comes up.
Also alot ads running in all using the ad blockers from Samsung plugins can change settings to some to help out on phone too. But they should just not allow ads from java, or flash and all that. Whole it helps with
This is caused by some third party app that was installed onto your phone.
Go to 'settings', 'device care', 'battery', and 'battery usage' to see what apps are running and using battery. Look to see if there are any apps you either don't recognize or don't want.
Then go to 'settings', 'apps' and disable/uninstall any apps that you don't recognize or don't want. This should definitley help with the ads.
After you have removed the apps make sure to clear your cache partition as they can leve behind some junk data.