What to do if Galaxy S9 restarts on its own while inside the pocket

Today’s post talks about a certain problem that many Galaxy S9 users may have encountered: random restart. While not as severe as other issues, a device that restarts on its own can sometimes be annoying, especially if you don’t have any idea why. In this short guide, learn how to handle this issue by following our troubleshooting steps below.

Problem: Galaxy S9 restarts on its own while inside the pocket

Hi. I have recently upgraded my Samsung from a s6 to a s9. I had the official Samsung clear view cover on the s6 and have purchased the same for the s9. When I am travelling with my phone in my trouser pocket, I will from time to time take it out, look at it and put it back in my pocket. The problem I am having is that on at least one occasion each time I travel, the phone restarts itself whilst in my pocket. I am using it in the exact same way as I was using the s6 so I don’t understand why this happening with this new phone.

Solution: There is no easy way to know what is causing your phone to restart automatically. You’ll have to work to identify the culprit. Let’s discuss the options that you can try below.

Check for overheating

Samsung Galaxy devices are designed to restart automatically when internal temperature reaches a certain level to avoid damage. If you tend to use your phone heavily while travelling, like streaming videos or playing games, and then putting it in your pocket shortly after, it’s possible that your phone may be overheating. Keep in mind that your S9 is a little computer but unlike its bigger cousins, it does not enjoy ventilation. Space in a smartphone is a luxury so any rise in temperature can easily spike inside. Certain tasks require heavy use which may lead to your phone’s motherboard reaching a certain heat threshold. This can trigger the mechanism that tells the system to shutdown or restart. If you noticed that your phone has become overly heated after using it, allow it to rest for at least 30 minutes by shutting it down.

Device may restart after an update

In order for new updates to be installed, your Android needs to restart. So, if your S9 happened to be downloading and installing system update while you were travelling, this may be the reason why it restarted on its own. Keep in mind that some firmware versions allow a user to set a schedule when a downloaded update can be installed. Try to check your phone’s update configuration under Settings menu to see if this is the reason for the unexplained restart. We don’t know the circumstances of your problem but this is worth checking. If your firmware provides an option for you to manually install an update of your own choosing, then we suggest that you use it to control when system updates are installed.

Bad system cache

Having bad or corrupted system cache can lead to all sorts of trouble although the main perceptible problem could be poor performance when loading apps. To minimize the chances of a corrupted system cache affecting the system negatively, we recommend that you wipe the cache partition at least once every few months. Doing so forces the device to rebuild the cache, which can be effective in getting rid of bugs.

To wipe the cache partition:

  1. Turn off the device.
  2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  3. When the green Android logo displays, release all keys (‘Installing system update’ will show for about 30 – 60 seconds before showing the Android system recovery menu options).
  4. Press the Volume down key several times to highlight ‘wipe cache partition’.
  5. Press Power button to select.
  6. Press the Volume down key until ‘yes’ is highlighted and press the Power button.
  7. When the wipe cache partition is complete, “Reboot system now” is highlighted.
  8. Press the Power key to restart the device.

Temporary bug

Sometimes, this simple procedure can fix bugs that developed after the system has run for a long time. By manually forcing your Note8 to reboot, you’re basically simulating a battery pull, which, in older mobiles with removable battery packs, was an effective way to refresh the system. If you haven’t tried this one yet, here are the steps that you can do:

  1. Press and hold the Power + Volume Down buttons for approximately 10 seconds or until the device power cycles. Allow several seconds for the Maintenance Boot Mode screen to appear.
  2. From the Maintenance Boot Mode screen, select Normal Boot. You can use the volume buttons to cycle through the available options and the lower left button (below the volume buttons) to select. Wait for up to 90 seconds for the reset to complete.

Poorly coded apps

Apps sometimes affect Android and interfere with its functions. If there’s a  more likely reason for your problem, it’s a bad app. However, knowing what app may be the culprit is not easy. There’s no diagnostic tool available for us to directly know whether a particular app is the problem. The most that you can do is to use observation and process of elimination to identify. There’s also no way of knowing whether or not our suspicion that an app is the real reason and not any other factors. If you noticed that the problem started to occur after installing a new app, it’s a good idea to uninstall it to see if that will make a difference. Once you’ve done that, you can then try to replicate the problem. Again, we have no idea how you’re going to do this but if noticed that your S9 seems to restart in a particular location before, you can try to go there after uninstalling the suspected app. This troubleshooting step can become tricky though if you have a lot of apps to test out so it may be impractical for you to do.

Software bug

In case there’s an unknown software bug that causes the problem, you can wipe the phone with factory reset. Make sure to back your files up ahead of time.

  1. Create a backup of your data.
  2. Turn off the device.
  3. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  4. When the green Android logo displays, release all keys (‘Installing system update’ will show for about 30 – 60 seconds before showing the Android system recovery menu options).
  5. Press the Volume down key several times to highlight ‘wipe data / factory reset’.
  6. Press Power button to select.
  7. Press the Volume down key until ‘Yes — delete all user data’ is highlighted.
  8. Press Power button to select and start the master reset.
  9. When the master reset is complete, ‘Reboot system now’ is highlighted.
  10. Press the Power key to restart the device.

Battery issue

We don’t have the full history of your device so we can’t say this for sure but one of the common reasons for random restarts is a bad battery. Since your S9 has non-removable battery pack, the only way to test our theory is by allowing Samsung to run some tests. If you think these restarts are bothersome and happens more often, you can contact Samsung so they can set up repair appointments for you.


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