I'd suggest that you do a PC Companion phone repair, this will do a clean installation of the latest firmware and will also wipe your internal memory. You'll need to back up your data before you proceed.
Open PC companion -> Support zone -> Phone/tablet software update -> Repair my phone/tablet (blue link style). Follow the steps given, do not connect your phone until prompted to press volume down while plugging USB cable.
You can always try to boot the phone without SIM- and/or SD-card to see if same behaviour appear. Otherwise, I suggest that you follow Questers advice to repair the software via PC Companion.
