Setting is located in BIOS under Advanced → Boot Feature → Restore on AC Power Loss.
The options are Stay Off, Power On, and Last State.
Use this feature to set the power state after a power outage. Select Stay-Off for the system power to remain off after a power loss. Select Power-On for the system power to be turned on after a power loss. Select Last State to allow the system to resume its last power state before a power loss.