Restart Xperia Z after Update

I have updated the Dirtyunicorn Rom and my device is working fine but from last day the device turn off and won't turn on by pressing the power button, so by chance i press and hold the power button along with volume up the device turns on it read all the apps and then display the home screen. This is happening after 3 to 5 hours. If this is a ROM problem than suggest me the best lollipop ROM and Kernal. And someone suggest me install stock ftf I dont know which region to install or which firmware i have .434 or .253