What do I do, my phone is about to die?

[Windows Central Question]

please help my phone about to die !!

hi
i have lumia 520 using wp preview 10586.107

after using about 2 weeks today my phone restarts endlessly... when it boots after about a min it restarts...
i tried soft rest and it didnt worked...
i also tried hard rest but it wont lunch !!! means the gears wont appear
finally i tried using win device recovery tool but after going to flash mode when a large mark of nokia apears after about two seconds it says operation ended with failure....
i guess it is something wrong with flashing mode?!
please help... my phone is going to die!!