15 R1, restart after sleep or shutdown

My 2-month-old Alienware 15 bought online from dell.ca always restarts after shutting down or Sleeping. Some similar problems found online but my case is more serious. It restarts even when I unplug the power and use battery only. I thought it's a software issue so that I have already followed the instructions online by updating &restoring BIOS, restoring power management sets, disabling fast boot, disabling automatically restart after failure,  disabling Wake-on-Lan, checking the powercfg-lastwake, reinstalling win10 operating system, removing static electricity. All those possible solution didn't work. I ran the DELL diagnose test but all hardware components passed. I didn't really believe the that test so that I installed a Linux system, in which the issue persisted. This problem occurred one day when it couldn't boot up after using up the battery, even though the power adapter was connected and had already charged the laptop for 2 hours. It finally turned up surprisingly one day later but the new issue came out that it couldn't normally shut down.  Are there any other possible solutions? Must the motherboard be replaced? Help!