If you are using multiple sticks of RAM, then try each individual stick in each slot (one at a time) and see how it goes. You could also change the thermal paste on the GPU and CPU if these are possible as a means of reducing temperature related problems, as these can cause freezing and restarting etc. Also,how old is the PSU, and does it have the necessary connectors. Using adapters, especially for the graphics card, cause power related problems.