I have Mikrotik routerboard 600a and it seems to have a serious problem.
It boots up, does beep which means it is starting up , then it does beep beep which means it has booted up and 1-5 sec after booting up it reboots. Like an endless cycle.
connect a serial cable, and watch in a serial console program what it does before it reboots. maybe there is a software crash. a reinstall would help, but you need to see it on the console to confirm