WK77, In the BIOS under SYSTEM SECURITY, you have AC POWER RECOVERY. If you set that to ON and set your delay if wanted, then the server will power on when it has power restored to it.  Let me know if this is what you were referring to.
Hallo!  I have a PowerEdge R710  server and trying to configure it to start when the main power supply switch in the 19" case is switched ON. No luck, there isn't any options in BIOS. Is it possible at all? Will be grateful for any suggestions... 
Wake up the PowerEdge R710 on power supply switched ON