anav, you're like a dog who marks every tree it walks by, but instead of trees you're marking forum topics
not really necessary as sindy kind of adviced/requested the same thing..
Plugpulled, regardless of the actual cause of the issue, which should be fixed anyway, you can get auto reboot using watchdog.
https://wiki.mikrotik.com/wiki/Manual:System/Watchdog
First, find a stable IP address, e.g. the remote address from the PPPoE interface. Or 1.1.1.1. Make sure the IP is pingable from the device.
Then, set the IP as watchdog address. As soon as the IP is unreachable for the time specified (by default: 1 minute), the device will reboot. There is an extra 5 minute wait time before the first subsequent reboot to make sure the device is slowly rebooting as long as the network is unavailable.
/system watchdog set watch-address=1.1.1.1 ping-timeout=5m