Share your experience!
Its a software related issue.This is the same issue as the "Power Button doesn't bring up the display instead just giving up a black screen".And for your case it might be blinking because the phone might not receive the current properly(try charging it with USB on the PC).
Your welcome.This is common issue faced by almost all Xperia SP owners(including me).By the way,may i ask you,what's your current firmware?
Oh,thanks.Yep,you should not update your phone now because it might cause some other issue.Just wait for the 4.3 update coming this mid december.
Woah,way off my knowledge.Sorry,but i don't know anything about system block.I'm so so sorry.Sorry,again.