How to fix a Galaxy S9 Plus that restarts randomly or reboots on its own after an update

One of the common problems that many Samsung Galaxy owners encounter is random reboot issue. In today’s troubleshooting article, we’ll address two cases of random reboot issues on the #GalaxyS9.

Problem #1: What to do if Galaxy S9 reboots on its own after an update

Hi. Recently updated my S9 yesterday and out of the blue started having issues. Apps (Twitch and Snapchat) were taking really long to load. Decided to restart my phone but after I did, it began to automatically reboot and would get stuck in the loading screen. I’d get to the Verizon loading screen and it’d start rebooting again. Tried to start my phone in Safe Mode but it wouldn’t work. Tried wiping the cache and doing a hard reset. Still nothing. Same problem…constant rebooting. After performing the hard reset, there was 1 time where I was able to get through the initialization/setup process. It worked normally for ~5 minutes but then rebooted again. Tried to flash my phone with the stock ROM through Odin. The reformat seemed to go fine but still having the same problem – rebooting without me prompting it. At my wit’s end. Don’t know what else to try. Only thing that I can think of is that the stock ROM had a different PDA/CSC. It was still a SM-G935V (like mine) but the PDA/CSC was slightly different. Not sure if that makes a difference. Thank you!

Solution: You’ve already done all the possible software solutions on your level. If the phone still reboots on its own even after flashing the stock firmware, that means the problem is most probably beyond your ability to fix. In some cases, we’ve some Galaxy devices reboot repeatedly due to defective battery. We understand you can’t just swap the battery with a new one on your own without tampering with the hardware so sending this device to Samsung makes sense. If the cause is not battery-related, then it may be something in the motherboard. It can be caused by bad Power Management IC (another common cause). Whatever the true cause is, we don’t think you will be able to identify it yourself without proper training and equipment. For this reason, we strongly recommend that you let Samsung handle the case.

As long as you did not tamper with both software and hardware, you should be able to let Samsung fix the device for free. Bring the device to your local Samsung dealership so they can examine the phone for you.

Problem #2: How to fix a Galaxy S9 Plus that reboots randomly

I have an S9 Plus and it just restarts at 2-3 minute intervals. At first my phone was not even passing the Samsung logo. It would just freeze on the first two letters of the samsung logo and it would restart all over again. At some point the device’s screen would become dead while still flashing the notification LED and i would have to wait till the battery to drain to start the phone again. So I took the phone to a repair shop and they flashed it. So now i have this restarting issue. Any suggestions on how to proceed?

Solution: If this problem started after someone modified the software, even when using official firmware, then the issue may be due to a software bug or an app. To fix the issue, these are the troubleshooting steps that you can try:

Clear the cache partition

Updates sometimes corrupt the system cache. We suggest that you ensure your phone’s system cache is in order by doing the steps below first:

  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.

Install Android update

We assume you have a carrier-provided device so if your S9 was flashed during repair, it may be running an older Android version. Be sure to manually check for Android updates under Settings > Software update. Updating the operating system to a newer version may help in fixing the problem. Newer Android versions may be more stable than the previous iteration so this might help.

Update your apps

Just as installing newer Android can potentially fix bugs, making sure that all apps are up-to-date may achieve the same goal. Whether you have a problem or not, it’s always good practice to keep apps updated. Be sure to check Google Play Store app for updates.

If you have some apps from outside the Play Store, we suggest that you keep them updated and ensure that they are compatible with the operating system. Contact their developers if you don’t know how.

Observe in safe mode

As mentioned above, one of the possible causes for your problem may be one of the apps you installed. To check if that’s the case, you want to restart the phone to safe mode. In this mode, no third party app will be allowed to run. With only pre-installed apps working, it should help you determine if our suspicion is correct. Basically, once the phone has booted to safe mode, the only other thing that you want to do is to observe it. If the phone becomes stable and won’t reboot on its own, you can bet you have an app problem.

To boot to safe mode:

  1. Turn the device off.
  2. Press and hold the Power key past the model name 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. Safe mode will display in the bottom left corner of the screen.
  7. Release the Volume down key when you see Safe Mode.
  8. Observe the phone for a few hours and see if the problem is fixed or not.

If your phone won’t reboot on its own during the observation period, you need to narrow down the possible causes. Here’s what you need to do:

  1. Boot to safe mode.
  2. Check for the problem.
  3. Once you’ve confirmed that a third party app is to blame, you can start uninstalling apps individually. We suggest that you begin with the most recent ones you added.
  4. After you uninstall an app, restart the phone to normal mode and check for the problem.
  5. If your S9 is still problematic, repeat steps 1-4.

Factory reset

The last troubleshooting that you can do is to wipe the phone and restore all software information to their defaults. After wiping the phone, observe it again for a few hours. If the phone is stable and won’t reboot randomly, then that means that a software bug or app bug may have developed which was the reason for the problem. If the problem stays even after you reset the device, that’s a telltale sign of a hardware malfunction. In this case, you want to send the phone in for repair or replacement.

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