How to fix Samsung Galaxy S9 Plus that reboots on its own randomly (easy steps)

Random reboots are often due to some firmware issues. They often occur after an update but there are times when they occur without apparent cause. Such is the case with some of the owners of the new Samsung Galaxy S9 Plus. According to some of our readers, theirs phones started to reboot randomly regardless whether they were using their phones or not. There were those who said the problem started shortly after an update as Samsung rolled out updates to patch some things up about a week ago.

In this post, I will walk you through in troubleshooting your Galaxy S9 Plus that reboots on its own. We will try to look into each possibility and rule them out one by one until we can fix the problem. We don’t know for sure how serious this problem is but if it’s just due to some issues in the firmware, you can fix it on your own without any help from a technician. So, if you’re one of the owners of this phone and are currently experiencing similar issues, then continue reading as this post may be able to help you fix them.

Before going further, if you found this post because you were trying to find a solution to your problem, then try to visit our Galaxy S9 Plus troubleshooting page as we’ve already addressed most of the commonly reported issues with the phone. We’ve already provided solutions to some of the problems reported by our readers so try to find issues that are similar with yours and use the solutions we suggested. If they don’t work for you and if you need further assistance, fill up our Android issues questionnaire and hit submit.

How to troubleshoot Galaxy S9 Plus that reboots on its own


The course of our troubleshooting will start from observation stage wherein we have to do a few things to find out if the problem occurs at certain situations. With that said, here’s what I suggest you do about this problem…

Run the device in safe mode and continue using it

We don’t know what’s causing your phone to reboot on its own so you have to try running it in safe mode and continue using it in that environment. While in safe mode, all third-party apps are temporarily disabled and only pre-installed apps and services will work. If the problem doesn’t occur in that mode, then it’s clear that there’s an app or two that’s causing the issue and triggering the reboot. To fix such issue, you have to find the app and uninstall it. But first, here’s how you reboot your S9 Plus in safe mode:

  1. Turn the device off.
  2. Press and hold the Power key past the model name screen appearing on the screen.
  3. When SAMSUNG appears on the screen, release the Power key.
  4. Immediately after releasing the Power key, press and hold the Volume down key.
  5. Continue to hold the Volume down key until the device finishes restarting.
  6. When Safe mode appears in the bottom left corner of the screen, release the Volume down key.

Continue using your phone in this mode and if the problem is fixed or doesn’t occur anymore, find out which app is causing it and uninstall it.

  1. From the Home screen, swipe up on an empty spot to open the Apps tray.
  2. Tap Settings > Apps.
  3. Tap the desired application in the default list.
  4. To display preinstalled apps, tap Menu > Show system apps.
  5. Tap UNINSTALL > OK.

Determining what app is causing the problem is often a challenge to many users. So, you must uninstall apps that you recently installed first or those that you installed prior to the problem. However, if the issue continues even in this mode, then move on to the next solution.

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Run S9 Plus in Recovery Mode and wipe cache partition

Another mode you need to run your phone into if the problem still occurs in Safe mode is the Recovery Mode or Android System Recovery. While the phone is inside that mode, you have the option to do some troubleshooting procedures that have a great impact on the firmware and probably fix firmware-related issues especially those that started after an update. The first thing I want you to try in this case is to wipe the cache partition. It basically deletes all system caches but once the phone reboots, they will be replaced with new ones.

  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 Android logo displays, release all three keys.
  4. An ‘Installing system update’ message will show for 30 – 60 seconds before the Android system recovery menu options appear.
  5. Press the Volume down key several times to highlight wipe cache partition.
  6. Press Power key to select.
  7. Press the Volume down key to highlight yes, them and press the Power key to select.
  8. When the wipe cache partition is complete, Reboot system now is highlighted.
  9. Press the Power key to restart the device.

Your phone will take a little time booting up after the cache partition is wiped off of its contents as it will rebuild or recreate those caches. Continue using your phone and closely observe it to know if the problem still occurs and if it still does, then you really have to reset it.

Backup your files and data and reset your Galaxy S9 Plus

A reset will fix most of the firmware related issues including this one. However, we’re always hesitant to suggest it because there’s no guarantee you won’t lose some of your files during the reset as it deletes all personal files and data saved in your phone’s internal storage. At this point, you have no other choice but to reset your device to fix the problem. So, take time making a backup of your important files and data. You may copy them over to your SD card or transfer them to your computer. Before you actually reset your phone try to remove your google account from your phone so that you won’t be locked out of your device after the reset.

  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 data / factory reset’.
  5. Press Power button to select.
  6. Press the Volume down key until ‘Yes — delete all user data’ is highlighted.
  7. Press Power button to select and start the master reset.
  8. When the master reset is complete, ‘Reboot system now’ is highlighted.
  9. Press the Power key to restart the device.

As long as the problem isn’t due to firmware modification of any sort, a reset will fix it. I hope that we’ve been able to help you one way or another. If you still have other concerns you want to share with us, contact us or leave a comment below.

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