Nuvi 350 occasionally shuts off

Have you tried resetting the gps? Also clean the contacts on your mount. That might have an effect on it.

Are you sure it is shutting off? When I have mine on Battery power, it appears to shut off (in bright lite) but it is really just dimming the display. When you touch the screen, or when it needs to give you new instructions, it will light back up again. If I have it plugged into the power jack, it doesn't do this.

I had exactly the same problem with a new Nuvi 250W. It shut itself off in the middle of a ride even though it was not recalculating. I also noticed it shut itself off twice just as I arrived at my destination.

I returned the unit and got a replacement unit and no problems since then.

Try having a look at the "Shutdown Error Reports" page. This may give some clues.

1. Power on while holding bottom left of screen.
2. Say "Yes" to starting in Maintenance Mode.
3. Choose "View Diagnostics"

Shutdown reasons are given on the first page.

(Assuming 350 is same as rest of 3xx range, otherwise see manual!)

My 350 did that a few times when I first got it. It seem to shut off just after or during a turn, and it had to recalculate. I updated the firmware and later changed vehicles. Hasn't happened since. Not sure if the firmware upgrade fixed it or maybe I had a corrupt vehicle file. I've had the 350 for 3+ months now and it has not crashed or turned off once since then. If in doubt, delete all the vehicles in your vehicles folder. You can always download them again using WebUpdater if that doesn't cure the problem.