Help Sony Xperia U (ST25) stuck in bootloop


I have sony xperia U (ST25).
The phone seems to be stuck in boot loop.
I took out the battery and reinserted and switched on the phone. The phone would attempt to start (could feel vibrations), sony logo does not come up and then the phone restarts all over again.

I tried connecting the phone to PC Companion but the due to restart issue, the phone will be detected by app for a second and then disconnected due to restart.
I could hear the sound of device being connected to USB.
The device connects and disconnects continuously.
So this make PC connection pretty useless.

Please assist with the issue.