my iphone 3g shuts down for no reason

Try a normal restart and if that doesn't correct the problem, try a reset.

Restart iPhone: Press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone back on, press and hold the Sleep/Wake until the Apple logo appears.

Reset iPhone: Press and hold the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears.

My 3G has done the same. I have tried the soft reset and obviously the simple power cycle. I have not noticed any particular activity that causes it. I've been talking on the phone, I've been typing an email, I've been using an application (different ones).

I have just done the phone restore (power/home buttons for 10 seconds) I will advise if this solves the problem.

My last resort will be to restore it to factory settings and then reload all my apps, music, video etc.

Short of that, I think I might be in the market for a 3GS.

Hi, I've had the same issue since the os3 upgrade:
iphone oddly (no drain at all, as I would have expected on normal days) indicating a full battery all day long then suddenly shut down. By plugging it to the power adaptor, the battery showed a very thin red bar. I had to wait a couple of minutes for the phone to charge up a little then I could start it up again.
Might be a bug in the battery charge indicator saying the charge is ok while it's actually very low?

I do experience the same problem with my new iphone 3gs 32gb.

it suddenly shuts down in the middle of using it and gives me the red battery sign when i reconnect it to power/usb without actually restarting. it just seems to need this initial charge for restarting (wont start by pressing any buttons/buttoncombinations).
i then unplug it immediately, replug it again and it will boot again (showing the apple and so on...)

doing a restore doesn't seem to solve the problem.
i'd really appreciate a solution to this problem.

cheers

This matches my experience: restart, reset provide no relief from random yet persistent unrequested shut down requests. Sudden loss of battery power. This started happening after the most recent software update. Coincidence?

Determine the following:

- If your Battery life approximate? Charge through Wall Charger for ATLEAST 2-3 hours then monitor it.

- Is there an application that you are running while this occurs? If it's a third party application, Delete it then Reinstall it.

- During calls: are you sure it shuts down? Maybe unresponsive at Proximity Sensor or a Leather case, a smudge, can be blocking the sensor.

- Has any liquid been in contact with the iPhone?

- Do a Restore as New, it could be that your OS3.0 download was corrupted, redownload the update and install it again on your iPhone making sure you have created a Backup of your contents - once the Download and Update has been completed you will be able to Restore from a Backup as the Backups do not have firmware on them.

Goodluck.

Tried the battery thing. No change.

No third party application in use at time of problem. Unless one considers AT&T phone calls a third party application.

It's not that the phone shuts down during calls, but that it wants to. Now, attempts to make calls in the first place fail, and when I pull the phone away from my face, I get the request to shut down (by sliding a cursor across the screen).

No liquid.

I restored as new and reinstalled from the backup. Things seemed to improve, but the phone is hypersensitive to movement. It buzzes at the slightest touch, including when I bring the phone up to my face during calls. And now, I can't make calls because it wants to shut down.