Nas unreachable

I have NAS always active but it happens that after 15 or 20 days, for no apparent reason, the NAS becomes unreachable.
No ip address is assigned, as if it were completely off. I have to turn off the power and restart manually and it starts again without problems.
How could I solve it?
No ip address is assigned, as if it were completely off. I have to turn off the power and restart manually and it starts again without problems.
How could I solve it?