iphone 3g strange issue

[Trranceman]

hello people, i am having an issue with my iphone, it shuts down itself while on standby(sleep mode) it shuts within a few seconds after it is set to sleep mode, once i had this kind of problem, i am not new to the iphone so it seemed to me to have a hardware problem so i took it to service center but i was wrong they told me that it was software problem so they fixed it, now i am having the same problem with another phone and i dont know what to do with this, i searched around the internet but nothing helpful, any help will be appreciated, thanks

 

[Applejuiced]

Try doing a restore again and setup as new phone.

 

[Trranceman]

No not worked :S

 

[Applejuiced]

Might be a hardware issue then.

 

[Trranceman]

no not hardware, it has happened after restore, i am sure

 

[Applejuiced]

If you restore a bunch of times and setup as new and it still does the same I doubt its a software issue.
But bring it to Apple if you want and have them check it out.