M21 phone switch off and on automatically

[mukesh1807]

My m21 phone is switching on and off automatically. Phone is more than 3 year old. Even technician is not able to identify problem.

[AvishekG]

🔧 1. Basic Troubleshooting (Try These First)

✅ Check for Software Issues

Safe Mode: Boot into Safe Mode to check if a third-party app is causing the issue.

Press and hold the Power button → tap and hold "Power Off" → Tap "Safe Mode".

If the phone is stable in Safe Mode, it's likely a bad app. Try uninstalling recent apps.



✅ Factory Reset (as last software resort)

Backup your data first (if the phone stays on long enough).

Settings → General Management → Reset → Factory data reset.

Or use recovery mode: Power + Volume Up + USB cable connected → "Wipe data/factory reset".



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🛠️ 2. Possible Hardware Causes

Since even a technician couldn’t find the issue, it's likely one of these hard-to-diagnose problems:

⚠️ Battery Degradation

Over 3 years, lithium-ion batteries degrade. A failing battery can cause random reboots.

Replacing the battery (₹500–₹1200 INR) might solve the issue, even if it doesn’t seem swollen.


⚠️ Motherboard / Power IC Damage

Common in older phones or those exposed to heat/moisture.

This requires board-level diagnostics. Repair may not be cost-effective (~₹2500–₹5000+).


⚠️ Loose or Damaged Internal Connections

Over time or due to drops, connectors can loosen or get corroded.

A deep internal cleaning or reflowing parts might help, but this is advanced repair.



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🔋 3. Signs It's Time to Replace the Phone

If:

You've reset it,

Safe mode doesn't help,

Battery replacement doesn’t fix it,

And it's still rebooting randomly…


Then the mainboard or another internal component is failing, and replacement may be a better investment than repair.


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💡 Recommendation

1. Try battery replacement if not already done. Cheap and often fixes random shutdowns.


2. If battery doesn't help, consider data backup and move to a new device.


3. If you're attached to the phone and want to keep it, look for a specialized board repair technician (not just general mobile repair guys).

[mukesh1807]

Technician said, battery is Okey, switching on and off in safe mode too, done reset, done. Software updates.

I think it's time to replace phone

[jay280]

One of 2 things

1. Motherboard got
🔥cooked 🔥

2.🔋 Battery is old and degraded you can get replacement if battery is the issue

[cs_member10]

Dear Samsung Member,

Greetings from Samsung Customer Support!

We regret to hear about your experience with our product. Please believe that this is not a usual occurrence.

Please perform the below-mentioned troubleshooting steps, these may help in resolving your concern.

Note: Kindly use genuine Samsung charger.

1.Disable auto restart function, there are two methods to disable auto restart function:
Settings > General management > Reset > Disable Auto restart (if enabled).

If the issue has not been resolved, then follow;

2.If you are facing this issue after installing any new application, then uninstall that application:
Settings > Apps > desired app > Uninstall > OK.

3.If the issue is still not been resolved then, update software:
Go to Settings > Software update > Download and install > Checking for software update > Software update available > Tap on Download > Downloading updates > Tap on Install now
Note: Your phone will restart after the update is installed.

4.If the issue still persists, then reset the settings: Go to Settings > General Management > Tap on Reset > Tap on Reset settings.

5.If the issue is still not been resolved, Reset the device:

IMPORTANT:
• Kindly create data backup of your device via SMART switch mobile application or http://www.samsung.com/in/support/smartswitch pc suite.
• Remember google password before resetting the device because it is required during initial setup.
• If you do not remember it, then reset (Forgot password) your google account.
• For this:
• Open Gmail (https://accounts.google.com/servicelogin) > forgot password >Select ""try another way"" > Next > Enter a new password > Next

Please follow the below steps to reset the device:
Settings > General Management > Reset > Temporary cloud backup or External storage backup > tab on Factory data reset (This will erase all data, including files and downloaded apps)

If the issue still persists, after performing all troubleshooting steps, would request you to please visit the service center. Below is the link to find nearest service center
http://www.samsung.com/in/support/servicelocation/

Warm Regards,
Samsung Customer Support