Xperia E3 reboots automatically topic

Hi there.
My Xperia E3 D2203 has one week old and, for no reason, it reboots automatically and sometimes it reboots continuously.
Before it reboots a message on the display says "SIM card inserted, Rebooting". But I didn't inserted or removed the SIM card, I even weren't touching the phone...

Please help!!!!!