Hi,
Well according to this Post #67
http://forums.windowscentral.com/nokia-lumia-930/328279-3.htm#
Its a hardware issue.... :(
Yes - it's hardware issue and I gave my phone to Telenor service. They sent it to Microsoft and after 10 days I got brand new device. Now everything works perfect. Before I also had overheating problem and some other bugs appeared but the new phone is absolutely OK.