I've seen a couple of people here talk about trouble with their phones that was solved by uninstalling a battery saver app that they had downloaded. I just read this article:
It suggests that popup ads for battery apps (which apparently often appear in games) can sometimes cause the app to download merely by touching them; and that some of these apps not only don't work but are security risks, stealing your contacts, phone IMEI number, and other data you don't want to lose control of. The article is worth a read, I think, especially for people like myself who are new to these phones.
Thanks for the tip. I'm very careful about what I download - scary to think something could get downloaded by accident while playing a game. Just read the article - thanks again!