After I installed new ram in my computer (replaced old 4gb stick with a new 8gb stick) I've experienced random computer shutdowns while playing fallout 4 (it worked perfectly fine before). I've heard that this can happen when the CPU overheats but I've used open hardware monitor while playing and monitored the temp and it never exceeded 55 degrees Celsius before it shuts down. Also when I replaced the ram I used compressed air to get rid of the dust inside the computer case.