do you overclock your PC?
what does the temps say?
do you use XMP?
use a custom fan settings in either radeon drivers or use msi afterburner without the statistic option installed, and make sure msi starts up at pc start.
Don't use both at the same time, use one or the other.
When using radeon, make the fan settings keep under 80 degrees and make sure your fans spin at full speed before it even gets to 80 degrees, safe it as your custom default and reboot the pc(you have to reboot to make it stick as default).
If your radeon keeps resetting it self, start using msi afterbuner as mentioned above and keep under 80 degrees make sure your fans spin at full speed before they reach 80 degrees,and stay clear of radeon fan controls and also don't use radeon chill, chill is bugged!