Why does my Galaxy S5 keep opening adverts?

I recenlty bought a galaxy S5 and i have a couple of apps on it(all from the appstore) and today it started opening the browser and going on adverts(such as Sky TV, or opening games in the appstore) after i unlock it and i have no idea what to do. I tried 3 different antivirus programs, cleaning up my cache, closing extra apps and still nothing.

Please help, thank you.

Welcome to Android Central! Try booting into Safe Mode, which prevents 3rd party apps from starting up. Then start opening apps one by one, and see when that behavior recurs. Reset: Samsung Galaxy S 5 | T-Mobile Support