Hi @adorpower , this can be tricky to track down… Grab a USB-Serial adapter to plug into J1, make sure to log the data… Beagleboard:BeagleBone Black Serial - eLinux.org
We have a patch in our version of u-boot, that reports the value stored in the watchdog to help clue in what caused the reboot… This might also log what the system did.
Side note, are you powering it via USB or 5Volt DC?
Hi Sir, we are using 5v DC
Well that solves one of the common “USB” sleep reboots that can happen…