did u install an unusual app, maybe by mistake u did press the power key. see in samsung phones it is built in, that if system feels that there is something wrong it will go off or restart. happened in alot of devices dont worry this is normal. but do check if u have installed an app which should not be there. also check for auto restart function.
A. Clear Wipe Cache Partition. Steps to perform. 1) Turn off the device. 2) Press and hold the Volume Up key and the spower button. 3) When the Android logo displays, release all keys. 4) Press the Volume down key to navigate and select "Wipe cache partition". 5) Press Power key to select. When the wipe cache partition is complete, Select Reboot System. 6) Press the Power key to restart the device.
B. go to safemode and observe is there same issue in safemode too if not then problem may due to other downloaded apps and if same issue in safemode then try to visit service centre
steps to turn safemode; long press on power button> long press on power off option>click on safemode >your mobile will restart and turn into safemode.
Keep in mind that in this mode only inbuilt system app will work
To enter safe mode, just press and hold the power button, just like you would when turning off the device. Once the power off icon pops up on your screen, tap and hold it for a second or two, select OK, and just wait for the device to reboot.
Another way to enable safemode ;
First, completely power off the phone. Then, power on the phone and when the Samsung logo appears, press and hold down the Volume Down key. If done correctly, "Safe Mode" will display on the bottom left corner of the screen.
