Hi Wake8825!   I think your internal battery is suspect.  I have seen this before and I also spoke to Garmin and they concurred.  If you are on ships power, note that a cigarette lighter connection is the worst electrical connection ever devised.  If your internal battery is weak and you have any interuption of the external power, even for a second, the unit will shut off.  Do you push the cig adpter in when this happens before you press the on button?  In this situation,
the GPS should go back into start-up mode so this should be obvious.  The second scenario would be if you are operating on the battery and it is also "weak".  In this situation, if the battery senses a spike, it goes into defensive mode and shuts the display off.  Pushing the "on" button will bring the display back up and you'll be right where you were on the GPS when it went dark.  It could actually a combination of the two.  You think you are still on ship's power but the cig adapter has moved and your now on battery power and the spike happens and the display goes dark and you think the unit has shut-off.  The key is where is the unit when it comes back, at start-up or back in the same place?  In both cases, if you haven't changed your battery in a while, it's probably the culprit.  You can order a battery direct on the Garmin Website (Buy Accessories) or check-out "Batteries America" in Wisconsin!  They can usually sell you a better battery for less (800) 308-4805  Good Luck, Bob Hart, APG-Eastern Avionics