ハードウェアマニュアル によると、BIOS設定の[システムセキュリティ]画面でオプションを設定できます。
AC Power Recovery (Last default)
Determines how the system reacts when power is restored to the system. If
system is set to Last, the system returns to the last power state. On
turns on the system after power is restored. When set to Off, the system
remains off after power is restored.