Yeah I know about this issue, let me tell you once if you remove the two memory sticks which you fixed later your system will definitely come to its normal condition and it will not shut down automatically. Is this the issue only with the 3rd and 4th slot of the memory? I mean if you remove the memory stick installed in the slot 1 and 2 keeping the slot and 4 installed with the memory stick, does that shows the same issue or else the system stays normal. If its normal then definitely the issue is only with the other two memory slots i.e. memory slot 3 and 4. And if not then definitely it could be the heat issue due to the excess of the memory utilization which is somehow making the process and the system heat up. Try to check out various other combinations with the memory sticks and the slots to see where exactly the issue lies.