If I manually unload the kext the same happens(system reboots immediately). For some reason, that lead to kernel panic on shutdown. So I dig down on the issue and found that ALXEthernet is causing the reboot. I had a fully working build with above motherboard, Recently updated to High Sierra and it turns out that the machine is Rebooting on shutdown.
Building a CustoMac Hackintosh: Buyer's Guide
