Hi, 

Bought M7350 last year for $53 bucks. Now out of warranty. I am having the bootloop issue on my M7350 v6.2. I upgraded to V6.3 and it did not fix the issue. Did Hard Reset and all but to no avail. I tried searching existing threads about it and it seems that there was no clear resolution that was posted. I was saddened that this is happening to a quality/branded item up until to this day even issue existed since 2015 but still no define resolution shared publicly as of this writing. If there was one shared publicly, please show me the right direction. I have exhausted the search function and google to find resolution. If someone could help me, please response to this thread. Looking forward to your response. 
 

PS: I also noticed that when no sim card is inserted, the device start up smoothly and did'nt even rebooted.