IPhone4 6.1 Jailbreak keeps auto rebooting

Hey guys, It's just what the title says. I've got an untethered jailbroken phone for my Iphone 4 running 6.1. So, every time my phone shuts off or battery dies, when I hook it to a power source whether it be in the electric socket or my computer via USB, my phone jumps into a rebooting loop. It jumps back to apple logo, boots up and my unlock screen appears so I can put in my passcode. But, it won't let me finish and freezes and reboots again to apple logo and everything repeats until the phone overheats and shuts off cos the batteries died. Anything I can do to stop this vicious cycle? Cos my power button is worn off, it simply just wont work, and putting my phone in DFU mode is almost impossible if my phone keeps with this rebooting loop. Need heeeelp! Cheers.