Why does my iPhone randomly reboot?

This is a battery issue coming from low quality batteries. The low-quality batteries you buy for cheap on ebay usually do no pass OEM quality standards, and instead of being destroyed they are instead diverted from disposal and offloaded for sale through alternate channels to benefit unscrupulous factory workers.

These batteries do may charge, and may appear genuine, often seeming to be normal during initial operation, but they cannot provide consistent amperage during use. They are defective in their ability to provide the necessary current required to run the devices they are designed for. Consequently, whenever the phone attempts to draw too much power from the battery, the battery can instantly fail to provide the necessary current to run the device at all, and the phone will reboot.

The solution is to buy genuine batteries from Apple.

First of all go to Setting->General->About->Diagnostics & Usage->Diagnostics & Usage Data.

In here you can find all the logs from your phone.

Check if there is any log file ended with .panic.plist if you have this file it means there is a problem with ether the software or hardware.

First try to restore to any older backup that was working with no issues. If not working restore as new.

If this does not work as well you can check for HW issue:

In case you still have warranty Apple will replace your phone with no problem.

If not, open the back cover and disconnect all the connections to the motherboard (Do not remove the motherboard), and reconnect them back.

Sometime there is one of the connectors that is not well connected and this cause this reboots.

Hope this help it worked for me

;-)

I have had this problem where I work at XpressFix. You can see us at XpressFix iPhone 4S Repair or iPhone 4S Repair Orlando. Check to make sure the iphone 4s battery connector to the logic board did not come unsoldered. As is separates from the logic board it could cause a reset. Some DIY guys came in and had actually separated the phones induction point from the logic board. Though it was hardly noticeable, we could see underneath. It was barely bonded to the mother board on the iphone. Anyway, hopefully you had some luck with you precious Apple.