iPhone 4 keeps rebooting itself

[historicus]

Every few minutes(like 5) while in use the phone just shuts off suddenly and then reboots. I tried restoring in iTunes and it didn't fix it. I can't even get the thing to finish syncing without it turning off in the middle.

What should I do?

Oh and I've had the phone for 27 days, it's not jailbroken, and this just started happening tonight as far as I can tell.

Edit: Nevermind about the in use thing, it does it regardless of use or not.

 

[BlakeLiebenTH]

I've experienced a similar problem, although my iPhone is jailbroken, and it only seems to restart when I'm tethering the phone to my MacBook Pro.

Do you use tethering? Perhaps that might be what's causing our problems.

 

[historicus]

I don't use tethering. So far it's happened when using safari and twitter and when it was plugged into my computer(pc laptop). Usually every 3-5 minutes while in use.

 

[WyleCoyote]

My new iPhone4 started doing this, but only when connected to a car charger. Rebooted every 5 minutes and charged very slowly. I could use the car clock and literally count down to within 4 seconds of when it would reboot. Car charger was old iPod FM transmitter/charger. When I swapped out the USB-to-iPhone cable with the one that came with the phone it worked. Swapped the old one back in and now it works. I suspect a bad cable or poor USB connection.
The charger shows green LED with no phone connected, and alternated between redish orange and green when things were funky. Now LED is steady red/orange with either cable when phone is connected.

I wonder if there's some reboot protection built into the phone is the supply power source isn't "stable"?!?! I figure with a repeated 5:00 minute interval, the timing has to be due to the phone and even using the same charger parts, it works fine after reseating the USB connection. Pure speculation on my part.