Holding identity button should reset on iDRAC not the system. Can you check the logs in iDRAC and see any other event happened that time which caused system reboot. You can SSH to iDRAC and run the racadm commands to reboot iDRAC You can refer below article on different ways of resetting iDRAC. [URL] 
I have an R730xd with everything on it in proper working order. I have recently been doing some VM shuffling so added more drives in the front bay to create another Virtual Disk.  When I was done I got rid of the virtual disk, un-raided the drives in iDRAC and removed them. As soon as I remove a physical drive the Health and Drive lights start blinking.  I have found in the past that the only way to  get them to go away is to power the unit down and unplug both power supplies.  This is far from ideal in a server environment. Is there another way to reset the trouble light without powering down?
Resetting flashing orange light without power down