Hi,
RouterBoard 112
CPU frequency: 175 MHz
Memory size: 16 MB
Boot configuration reset, applying defaults
writing settings to flash... OK
Press any key within 2 seconds to enter setup..
loading kernel from nand... OK
setting up elf image... OK
jumping to kernel code
Starting...
Resetting system configuration...
Starting services...
I was tring to format nand and netinstall all from begening. Mem test show no probleblems.
Any ideas?
make sure you have not shorted any jumpers on the board. if some wire is touching the reset jumper, this will happen
I’ve taken from board pin reset and dip switch reset. So there is no way to short this.
Nice to have support … 
this is a user based forum, not a support system.
check if you don’t have any damage on the PCB board, maybe there is a scratch or some solder traces that are causing the resets. Like I said, the jumper is the only thing that can reset it. Either that, or some connection leading to it.