Have you any notifications on the notification panel that might help track down which app is sending them? If not booting into safe mode is frequently recommended because it temporarily disables any third party apps that might be sending them.
@BaldDaddy You may have downloaded a third party app that has bunch of ads hidden. You need to scroll your apps one by one and delete the ones that is suspecious.
BaldDaddy you are very welcome. I am glad that did the job. I would keep using the app every 4 days unless the ads get worst, then run it every other day. You have a great day