Why doesn't my phone work properly?

[Kinganimepie]

My phone is a Samsung galaxy light. I was using it yesterday and it restarted byitself. I know that not normal, after it finished restarting it function normal for a while(10min). Afterwards it start to restart again then it did again. I try doing a master reset and a hard reset but that made the condition worse. Now it stay on the Samsung logo and vol key up + home key + power key, goes to a downloading don't turn off target screen. can someone please help me?

 

[B. Diddy]

Welcome to Android Central! Have you tried a different battery yet?