My edge suddenly developed the habit of constantly shutting down. I had gone through all the forums but no one seemed to offer a solution. I broke my rubber power on off button trying to do hard resets, and so on. I now have to turn it on and off using a pen.
OK - so I thought I had broken the power button so I had nothing to lose. I connected my Garmin to my computer and displayed all the folders in MS Explorer. I then deleted EVERYTHING (folders included). NOTE: you will lose all your activities but mine are all loaded to Strava anyway.
I disconnected the garmin and powered it back on (using the tip of a pen!). ... Guess what... My Garmin was back to normal and WORKING. I have to reconfigure my screens to how I want them but the Garmin reconnected to my phone and my radar with ease and it didn't power off. I was even able to update the Garmin via the Garmin app on my iphone and do the latest software update.
Goodluck!
Mail Star Espresso