In most cases the issue is related to the SD card as the recorder performs a disk check and if any issues are encountered it will either emit three long beeps and restart or simply restart/reboot.
If this happens with your recorder, power it down, remove the SD card and check it in a computer to see if it can be accessed as normal.
If so please check our support portal for advice on how to reformat and reinstall the software on it for your recorder model.
If the SD card cannot be accessed in a computer then replacement of the SD card is required.
These can be purchased from us with software pre-installed or you can prepare your own following the guidance on this support portal.