I have been facing this issue frequently now, and no solution up till now.

The issue is, my router board doesn't come up after Router OS upgrade. i have encountered this making the third time now with (RB SXT, RB760 and RB750).
The router shows led light signifying is powered on, but Ethernet connection to PC goes off and on.
It doesn't pop up in the neighbor discovery at winbox nor can you connect via any other login platform.
I tried basically the recovery processes; resetting, netinstall still to no avail.

Any advice on what can i do?

I encountered this same boot loop on a Metal 2 radio. Try using only ssh/telnet and don't even attempt to connect with winbox or http and see if you can get the device to stay up. If you can connect via console, see if you have kernel error messages.