IPhone 6+ rebooting in standby

Hi guys! I bought an iphone 6+ a few days ago, as soon as i got home i notice that it reboots when its in standby. I can use it for hours without any problems: wifi browsing, voice calls, camera, everyrhing works. When I put it in standby in 20-30 seconds it reboots. Now the other problem: when it reboots i got the apple logo 4-5 seconds and then it reboots again-sometimes after 5-10 cycles it enteres in ios-other times it keeps rebooting for 30-40 minutes. If i do a restore (ios 9.2) from itunes i got error -1 right at the begining of the restore and it kicks the iphone in recovery mode (on screen: cable and itunes logo). If I want to restore it again i get error 9. I used 3 original cables and tried the restore on 3 computers-same result. I did read that -1 error its a baseband error but i dont have any problems with imei. Any suggestions ?