I suspect disk problem,...
I found in system menu the check-disk command. WOW
I run it. But the only message I got is if I want to reboot the device.
If I accept when the device is restarted any info on log (write to disk enabled)
I searched info about check-disk usage on forum, wiki, manual... but nothing.
Someone can help me?

Why do you suspect a disk problem? Is it flash, is it a RouterBOARD? What version of RotuerOS is running on this device? You can try and connect it (if it is IDE, SATA) to a working RouterOS (may be in demo mode) and in WinBox -> Store (or System->Store) -> you will find a check-disk command there that checks a secondary drive without restart. But take care not to format it. Backup, save the backup to your (other) PC.

On ROS 6.35.4 there is no system check-disk?
How do i check USB attached disk?