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Sounds like a Bootloop see below for the probable fix
Try performing a system repair as this will often fix issues - This will factory reset your phone
Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds)
Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the onscreen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process
If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP
Did you connect the cable the correct way as you may have damaged the phone if not - because of this I can only advise you to contact Xperia care http://support.sonymobile.com/global-en/contactUs/
You should not be able to connect the magnetic charging cable the wrong way around since the contacts on the phone and on the connectors are harmonised to make them idiot proof... 