Hi everyone,
i need help with this phone

Since couple of days, my sony k850 phone ,when powered on vibrates for a second and then goes off,nothing on the screen, then vibrates again

i took off batery,memory card but still does the same

than i tried software upgrade,but it says your phone is already up to date

how can i rectify this probllem
how can i re write the software
after full charge only the keypad lights turns on thats it

Thanks
Prateek