Welcome to Android Central! I suspect some other app that you installed is causing this one to piggyback. Do you recall installing some other app around the time this unwanted one showed up?
You may need to uninstall your most recent apps one by one until you find that this rogue app no longer installs on its own. You could also install a good antivirus app like Lookout, but it won't necessarily find a true virus.
Posted via Android Central App--please excuse the brevity and any typos!