Rx 480 8gb problem

windows restart after randomly time period even i use ethminer for mining or just idle screen its restart

msi motherboard z97 guard pro
psu is corsair 750x 80 plus gold
ram 8 gb
intel dual core
1x xfx rx 480 8gb oc 1328
windows 10 64 bit with latest amd driver and also checked cd driver with card

and i am using powerd usb riser

i just checked in GPU-Z VDDC is 1.1313 is it normal??

kindly help me to solve this issue