CHECK VIRUS WHICH MAKE UR CELL RESTARTED.

If ur device restarted everytime when u try do something then ur device may infected with virus.there r many types of virus spread over bluetooth and GPRS with software.use fexplorer and go to this path
C/system/bootdata
if "lib" folder allready exist in it then its deffinetely virus and u cant delete this folder and if u try device may restart.there is only one way full format both phone and memory card.but u cant find "lib" folder then problem not very serious.