When looking at iPhone Home screen, iOS app icons randomly flickering or flashing without any indication what was the purpose.
Some threads suggested the app icon with "Cleaning" text was attempting to clear cache. In this case, no "Cleaning" text was displayed. Also saw a thread indicating there might be a log file called Panic under Diagnostic and Usage Data that was affecting the app.
iOS version 11.1.1, Settings > Privacy > Analytics and turn off Share iPhone Analytics. (So far, this seems to solve the mystery.)