How do I Start Dell EMC PowerEdge XR2 Server automatically when a power source i...

Is there a way to boot on a Dell PowerEdge XR2 server once power is connected to it, similar to how an Intel NUC can be?

(Required notice: I work for Dell)

What you likely want is AC power recovery.

Specifies how the system reacts after AC power has been restored to the system. It is especially useful when systems are turned off with a power strip. When set to Off, the system stays off after AC power is restored. When set to On, the system turns on after AC power is restored. When set to Last, the system turns on if the system was on at the moment when AC power was lost. The system will remain off if the system was turned off when AC power was lost. In case of an ungraceful shutdown, the system always turns on. Note:The host will not power up until iDRAC Root of Trust (RoT) is completed, host power on will be delayed by minimum 90 seconds after the A/C applied.

On the iDRAC it is under Configuration -> BIOS Settings -> System Security -> AC Power Recovery

In your case, you would want it set to On instead of the default of Last.