A display that lights up intermittently is usually the result of an intermittent loss of power, i.e., loose battery connection.  Remove the cover of your DIGI-WALKER pedometer or remove the battery cover of your NEW-LIFESTYLES NL-800 or NL-1000 accelerometer, and then remove the battery.  Pull up on the prongs that lie under the battery.  Reinstall the battery and the cover.