Default [Q] Nokia Lumia 710 is not starting

I have a unlocked nokia lumia 710. The problem was started when my battery was fully drained and my phone was unable to start. then I put the phone to charge , it showed battery logo for atleast 2 sec then the screen goes to black and after that phone gives a normal viberation ( normally when phone is swithched on ) and after few seconds phone gives a short vibration and then nothing happens. when I connected it with pc then it shows flash mode.
What should I do ? Give me some suggestion guys... please....