+ 0 Votes My first thought is over-heating... wizard57m-cnet Moderator 1 year ago So, you may need to do some cleaning. Clear the vents of any obvious dust, open the case, check for dust inside. A small vacuum helps cleaning up the dust. You can use cans of compressed air to aid in removal of dust as well.Next check the fans, make sure they are clean and freely moving. Then check the heatsink on the CPU. Might need to remove the CPU from the motherboard,use care and consult a guide (you can find these online with a search). One note,be sure you have a tube of thermal paste on hand, you will need this to reassemblethe heatsink to the CPU. Clean all the little vents off the heatsink, dust gets stuck in them quite normally. Reassemble and check all your RAM, cards, cables etc just to be sure you haven't got a loose one, then close the case cover and power on.Once it's booted, put it through a test by browsing a few sites, maybe even open a couple of browser windows, I wouldn't do anything that you would not want to lose if it did shutdown, but I'd stress test it. If all is well and it doesn't shut down, then you're good to go for awhile. If not, then you may need to consult a technician and have them check for failing components.