I've had my BlackBerry 8350i since November 2010. A few weeks ago it started randomly rebooting. Some days I will just see it reboot once, other days, it reboots continuously. I'm just thankful I haven't had some type of an emergency or been in a situation where I've had to use the phone when this happens since each reboot takes @ five minutes and sometimes it reboots three or four times in a row! I also stopped receiving emails and can no longer access the internet. I have contacted customer service a few times via chat and phone and noone has been able to fix the problem. They've suggested I go to an actual store, but I haven't been able to make it yet. The last person I spoke with finally said that, as far as the email/internet issue, I'm not receiving data. He figured that out because instead of NXTL, I'm only getting NXTl. He said the the "L" is that indicator of the data. Noone has had the answer to the rebooting issue. I called a couple of the stores near me that I will be taking it to have it looked at, and they both said they haven't heard of that issue so I'm guessing I won't have any luck there either. Anyone having the same issues?
For the restarting, the best bet would be to visit a Repair Center as you said. If you are not aware of where the nearest one to you is, its easy to look up at: www.sprint.com/storelocator and select "Repair Centers Near Me".
Now for the NXTL, that is a slightly different issue. If you haven't done it yet, go ahead and pull out of the battery with the phone still on. Leave it out for a good 60 seconds, then put it back in. This will give it time to reset the network connection. From the sounds of things, you don't need me to tell you it might take a while to come back up. Once it is up, look for that NXTL. That should atleast get your data working until you get into the Repair Center.