New i93Phone shuts down, or restarts at any time

Nov 30, 2012
I am on version 3.6.7 with a super clean install (english version only, no multi lang.) . I face only one very big problem that my phone restarts at any time without any reason. and from today, its just shuts down without any reason at any random time i remove my phone from pocket, its turned off. No offence to this fantastic ROM, but phone is used for calling, or to receive calls or sometimes emergency calls. I would have missed an emergency call . So whenever you guys make an update, make the essential functions of the phone such as calls, messages, etc. are working properly. THIS SHOULD BE YOUR FIRST PRIORITY. Coz the other party cannot hear my voice clearly when in a call. MIUI is the best rom in this universe. So i want to use this only. This was just a little request (opinion) from my side to you guys , PLEASE TAKE CARE OF THESE THINGS IN YOUR NEXT UPDATE.

My phone : samsung galaxy s3 gt- i9300
rom version : miui v5 3.6.7 english version