I have a 285WT that all of the sudden went into a reboot loop where it would start the splash screen and the "Loading Maps" and then reboot. I couldn't even do a "Master Reset" because the option didn't stay on screen long enough to select it. (Note: I was trying to do this while the device was connected to my PC via the USB cable).
On a whim, I put my camera's SD card in the 285WT's card slot and restarted it again. This time it stayed on and went into charging mode. I also had access to the drive letter in "My Computer" for the Garmin, so I was able to see and manipulate the file/folder structure.
Not knowing what was causing the reboot, I just let it charge for a couple of hours. I then turned it off, removed the connection to the PC, and then restarted it. Everything came up fine -- no issues.
I'll be monitoring the device to see if the reboot problem is gone for good, but for now this saved me from having to do a master reset (which I couldn't do when it was rebooting all the time, anyway).
Hope this is helpful.