Have you downloaded any apps recently or that were from another source besides play store , etc?
Do they appear in your notification bar ?
They could come from an app you recently downloaded.There are a few app that detect which apps use that method to push ads to your phone though notification bar .
One of those is : https://forums.androidcentral.com/e...d=com.lookout.addetector&hl=en&token=iphp5p15