Hi all,
I don't have a Android phone but a friend does who also experienced something similar to this has a couple of suggestions on how to sort it out.
1. Delete your browsing history, the issue may lie within a dodgy Adsense Advert but the root may still be within your History, so clear your browsing history.
2. My friend also said that he only experienced this when using Chrome on his phone. He downloaded a different web browser and didn't have the same issue.
If you haven't already it's worth trying the two suggestions above- I don't have an Android phone so I can't explain how to do it but there are many guides online that can help.