I have this issue too for some time now. Your laptop turns off because it is heating due to the fan not working. It is not the fan, i have replaced the fan and i still have the same issue. It makes a buzzing noise but nothing moves. The issue is there is not enough power going into the Fan for some reason and that has to do with the motherboard. I have not found the solution to it nor have found the solution else where. Not many repair shops knows how to fix a Vaio. If only i you can purchase a motherboard but they arent sold anywhere.