Brand new BeagleBone Black auto reboot

I am a new user to BeagleBone.
I have just bought a new BeagleBone Black. I have not modify anything from the original board.
I have a SD card loaded with QNX platform from the following link

I have tried to power the system with a 5V supply or USB connection, both of them randomly rebooted itself and the 4 USR led were on solidly.

Would you mind please help me what may cause the problem?

does the board reboot with the OS that shipped on it ?

if its fine, the software your using may not be dealing with the
watchdog timer.