The most common method of aquiring adware is through downloading an app.
To see whether you are using an app that renders advertisments you can boot your device into safe mode.This will prevent any third party software from running.Since i do not know which device you are using you can try this to boot into safe mode.
How To Boot Your Android Phone or Tablet Into Safe Mode
If the problem persists once in safe mode it is not an app.
If it does not persist you will have uninstall an app to remove the adware.
If the problem persists once in safe mode it is not an app.
Start by uninstalling apps that you did not get from the play store.
You may also use a mobile antivirus software to do the work for you i recommend
https://forums.androidcentral.com/e...etails?id=com.zemana.msecurity&token=gIXY3gcm
as no purchases are required
If the problem has not gone away please make an account and reply on this thread.