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Did you restore any back up after you performed a software repair? Or installed any applications?
You can always try to boot your phone into safe mode to see if you experience the same behaviour:
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008
Okay, in this case I suggest that you visit nearest service center so a technician can examine your unit. You can contact your local support team for information about nearest service center and/or how to proceed with this in the best possible way:
http://www.sonymobile.com/global-en/support/contact-us/contact-info/