iPhone 4S restarts itself often. Crash Report

For the last couple of months my iPhone 4S randomly restarts itself.
I have looked at the "Diagnostics and Usage" in the settings menu and it contains a lot of crash reports.
One of them says:
Hardware Model: iPhone4,1
OS Version: iOS 6.0 (10A403)
System ID:
2012-10-21 09:21:20 -0400 assistant_analyzer[127]: WWAN Preferred:0;Retry Success:0;User Failure:0;Gateway availability status:0

Can anyone decipher this?

Thanks in advance

Skibsted