Hi,
This is definitely possible - Quick example below:
Nexus3000(config)# show run all | i i poap
no boot poap enable
Nexus3000(config)# boot poap enable
Nexus3000(config)# end
Nexus3000# copy r s
[########################################] 100%
Copy complete, now saving to disk (please wait)...
Copy complete.
Nexus3000# reload
This command will reboot the system. (y/n)? [n] y
.....
You can see post reload my Nexus 3000 has entered the POAP prompt sequence once again:
...
Waiting for system online status before starting POAP ...
Starting Auto Provisioning ...
Done
Abort Power On Auto Provisioning [yes - continue with normal setup, skip - bypass password and basic configuration, no - continue with Power On Auto Provisioning] (yes/skip/no)[no]:
You can find this information in the N3K's PowerOn Auto Provisioning Guide as well:
"POAP can be triggered even when the startup-config is present using the boot poap enable command."
Hope that helps.
- Andrea, CCIE #56739 R&S