got this from the net, maybe it helps:
The Problem with Nokia 3110c – Switching off and automatically restartingThis is what happens. Nokia 3110 hangs, gets switched off andrestarts randomly. More often, it restarts around 3 times or so andthen gets switched off.
Possible Causes and SolutionsCause 1
– Phone Memory Full – Nokia 3110c mobile phone has got 9MB of internal memory.Solution
– Keep the free space between 350 to 500KB, so as to keep things running smoothly on your phone and preventNokia 3110c from restarting.Cause 2
– Changing Themes – Some people havereported that the phone restarts automatically when they try changingdisplay themes on the phone.Solution
– Don’t get your phone loaded with toomany themes downloaded from the internet or atleast, don’t switchthemes frequently. These themes, mind you, also load up things intoyour already falling Nokia 3110c phone memory.Cause 3
– Memory Cards – Some people have reported that Nokia 3110c restarts due to some issues with the memory card.Solution
– Remove the card, get it formatted and then insert it back and then restore factory settings. This just might solve the issue.Cause 4
– Transferring data via Blueooth / USB datacable (or) Updating Music Library – A few people have reported thattheir Nokia 3110c mobile phone restarts when updating the music library.Solution
– Don’t try updating of music library frequently or don’t often transfer data in/out of your Nokia 3110c phone.Cause 5
– MP3 filesSolution
– This may seem dumb, but considerconverting all your MP3 music files to WMA and then store them on thememory card. Some users suggested this.Disclaimer
– Follow the suggested solutions at your own risk. The author is not responsible for any damage caused to your phone.
UPDATE:IT LOOKS LIKE A FIRMWARE UPDATE COULD FIX SUCH NOKIA 3110CRESTARTING PROBLEMS – RESOLVE YOUR ISSUES RIGHT NOW BY UPDATING YOURNOKIA 3110C FIRMWARE – CLICK HERE
TO KNOW HOW YOU CAN UPDATE YOUR NOKIA PHONE FIRMWARE