A common malfunction of DVRs and NVRs is the device shutting down and turning on by itself every few minutes or half an hour.

Obviously, if your DVR / NVR keeps rebooting by itself, your security system can’t work properly. Usually the problems are connected to the device power supply or the hard disk drive, but there could also be other reasons that prevent the DVR / NVR from recording properly and cause it to restart over and over again.
  
The below checklist can help identify the cause of the problem that causes your DVR / NVR to reboot repeatedly before you contact your dealer / distributor for a replacement. 

When the voltage is unstable or lower than standard values, it can cause the DVR to restart automatically. For testing purposes, unplug the device from any battery backup power like surge protectors or UPS.
Check the device power adapter: make sure you are using the right adapter that can provide enough power for the DVR and that it is intact (make sure it is not the power adapter that is intended for a camera or Power over Ethernet (PoE) switch) . It is also advisable to double check the outlet the device is connected to: This is easy to do by plugging the DVR to another outlet and seeing if the problem persists. 
Power off the DVR, then Disconnect the DVR from any cameras and power it on again and check if the problem continues. 
Sometimes, the cameras might cause a short circuit. If the cameras are installed near high voltage, the system can detect incoming voltage and restart to protect itself (This problem is common with HD Analog CCTV using coaxial cables). By unplugging the cameras, monitors or anything else plugged to the DVR and then re-connecting them one by one you can determine if this is the source of the problem.  
If the DVR continues to reboot automatically, continue with the other steps in this check list.
 

A faulty HDD can cause the DVR / NVR to reboot, a simple way to check if the HDD is the cause of the problem is by disconnecting it from the system board. If the problem stops, then the HDD is the problem. Many DVRs have a fault detecting algorithm, if the recorder can’t recognize the connected HDDs, it will keep rebooting. Another potential problem is that a damaged hard drive draws more power than needed from the motherboard and may cause the recorder to shut down.
To check the HDD you will need to power off the device and open it up. Carefully unplug the HDD from any connections to the system board and test if the rebooting continues (there are 2 connections, one is the data connection and one is the power connection). If the problem stops, there is a need to replace the faulty hard drive. 
If there is more than one hard drive installed in the DVR / NVR, they need to be unplugged one by one to identify which one is causing the rebooting problem. 
Important note: DVRs and NVRs work best with dedicated surveillance drives. They will not work if you use regular desktop hard disk drives. Be sure to use a dedicated surveillance drive.
 read more: DVR Hard Drive Failures and How to Prevent Them

Over heating can cause your DVR or NVR to restart automatically. If you already opened up the DVR to check the HDD, it is advisable to check if the DVR fan is working properly. The fan cools down the processor on the system mother board. If the fan is not spinning, or is full of dust and other particles the CPU will heat up, causing the recorder to restart itself. Eventually, overheating can cause the motherboard to burn down and the whole system will have to be replaced. If the fan is ok, check if there are any external factors that can cause the DVR to overheat (e.g. bad ventilation, tight enclosure, other machines that radiate heat).

if there are no hardware problems, rebooting might be the result of conflicting settings. These can be  IP conflicts – if the NVR shares the same IP address as another device on the network, this might cause the NVR to reboot. Check if the system has auto-reboot settings – some DVRs are set to reboot on regular schedule (usually once a week), disable this function to check if this might cause a glitch in your system. Another thing to check is that your system is using updated firmware.
 
Is now the time to consider cloud based video surveiallance (VSaaS)? read our article:NVR vs. VSaaS: Exploring their pros and cons
 

 
DVR/NVR rebooting is only one of the problems you might encounter. We also wrote down a few other common DVR/NVR problems and how you can try and fix them.

This can happen if there is a loose connection somewhere: check that the camera power cable is connected firmly, or if the camera is not connected properly to the DVR back panel. Check if the DVR is connected properly to your monitor with an HDMI cable: the cable might be faulty or you might have plugged it in the wrong HDMI port. Check that the monitor is set to the right resolution, video loss might happen if the monitor is not set properly and can’t display the video feed.
 

Video feeds are saved on the Hard Disk Drive (HDD) of the recorder, the first thing you must check is if the hard disk is working properly. This can be the result of a faulty HDD, the drive running out of space, or a problem with the time and date settings of the DVR/NVR: if the time and date are not set properly, you will not be able to find the video you are looking for.
 

This is usually the result of an HDD problem: the hard disk drive is either faulty, not formatted properly or there is no HDD installed.