I have the same problem with my Nokia C7. It re-starts randomly, freezes during message typing/music/video playing then re-starts. It was doing it between 3-6 times a day. I took it back to the Vodaphone store and they suggested it sounds like a software problem. I took it to the service centre myself where they installed the latest software. That was on Tue 2/8/11 late afternoon. It was working great no problems for 2 1/2 days then this morning 5/8/11 it has restarted twice. As i was nearing the end of a lengthy message that was then lost i was very frustrated (actually ###### off). So i looked on Google and some forums to see if anyone else was having trouble and from what I have read it is a problem world over with many people having the same problem. Some suggest it is a Software problem with the Symbian OS, others suggest problems with either the SIM card, SIM card reader or SIM card software. Others have speculated that it is a hardware problem and that contacts in the phones board have not been soldered correctly. What makes me laugh (you have to I guess) is that these posts are from the offical Nokia Service Forum board, where numerous people have raised the same re-starting issue, and yet Nokia have not responded to any of these posts.
Apologies if i have bored you, but long of the short is i will take my phone back and try a new SIM card, then if that fails i will demand a new phone. I do like the C7 just want one that works.
