Help My phone keeps restarting

[Android Question]

When I remove the battery and put it back, it turns on automatically even i didnt pressed anything. I try to reboot it but it comes up in "a custom os can cause critical problems in phone and installed applications". I press volume up and it says downloading but its not. i have waited for a hour but nothing happens. What should I do? Please help me

 

[James L]

Was the device rooted? If it was sounds like you tried to update it.
Download the firmware for your device from sammobile and flash it with Odin.