Iphone waking from standby when on roaming or without sim card

[knalte-b]

Hi there,
I have a problem, my iPhone 4 keeps waking up from standby every 20 seconds as if I´d press the home button whenever I am on roaming or if I remove the sim card. This of course drains battery life like crazy. I tried different settings and restarts but all of this does not help. Furthermore sometimes when I receive calls the slide bar does not react when I receive calls.
I´d be happy if someone could help me with this, of tell me whether I should go to apple and have it fixed...

thanks!

 

[TEG]

It might be hardware, it might be software. I would highly recommend restoring the phone or taking it to an Apple Store. I had this problem with my original, and restoring the software solved the issue.

TEG

 

[knalte-b]

ok great I will definitely try that later, otherwise apple store it is...