Default [Q] Xperia Mini pro keeps rebooting,touchscreen dead

Hi guys...
My 1 year old xperia mini pro sk17i keeps rebooting automatically.The problem started when the touchscreen stopped responding all of a sudden.At first the problem occured only once in a while and then escalated.Now the touchscreen is completely dead.I could still operate the phone with the H/W keyboard,except for attending calls.Then a few days back,my phone has started to reboot automatically.This doesn't occur when i operate the phone while it was charging,but the touchscreen is still dead.I tried factory resetting the phone,software repair,flashing new ROM but this didn't help .Could it be a battery problem? Is there any hope to fix my phone?Any tips are appreciated.Thanks in advance.