iPhone4 keeps on restarting up to apple logo

[ahdhulla]

hi,
a friend of mine, brought his i4, it keeps on restarting up to apple logo. when he brought it, it was dead and when i put it into computer shows apple logo and goes blank and shows it again and keeps on ... its annoying.

I dont know what he did. He told it was on 5.1 and jb'd tethered. i have tried several things but still keeps on restarting. I can put it into DFU mode. but he needs to fix it without restoring if possible.

Is it possible to fix it? or is it battery issue?? Need your help Please!!!

 

[bandofbrothers]

Have you tried tiny umbrella to try and take it out of the loop ?

 

[ahdhulla]

when connect it to TU, device not recognised and keeps on restarting. So i put it into dfu mode exit recovery that show several lines in black scree. Last line says greenpois0n initialised. Nothing more.
I am not familiar with TU and need more details how to do so

thanks

 

[ahdhulla]

And the other thing is when i disconnect the device to goes dead black screen. No apple logo nothing. Does that mean it's a battery issue. even if its a battery issue my guess is it should be able to restart when the device is connected to computer.
this might be a silly issue but please help me on this.