Why does my computer shut off frequently without warning?

I am watching this question closely I have the same issue. Some have said its malaware, but I have run checks. Or overheating, but my fans are OK. I have also dusted the air vents.

Could be a bad power supply. Is this an old pc?

If it is a total shutdown and not just the application crashing it is probably from heat. There are little sensors inside that measure the temperature and if it gets to hot will instantly cut power to it. This is done to prevent damage to the hardware.

If it is a desktop I would take the cover off and look inside to see how dirty it is. I clean mine about every three months with a toothbrush and compressed air. I wouldn’t suggest trying to take apart a laptop. A professional would be best for that.

A little more information might be helpful. What Operating System?
If Windows, open the event viewer and look at the system logs as a start.

Make sure the fan is not choked with dust. Open the box and blow it out gently with compressed air. In many cases it means the processor is getting too hot.

First guess is heat simply because my experience is that is usually the case.

If heat can definitely be ruled out, then one may have to do a little forensics, as per @blueiiznh‘s suggestion, but 95% of the time it’s as simple as a heatsink full of lint.

@blueiiznh – If the OP is asking this sort of question, I think it unlikely that they know where or what Event Viewer is ;)

@jerv or what a heatsink is or where to find it.

@blueiiznh I understand what you are saying, but I think most people can figure that a big hunk of metal with a fan on it may have something to do with cooling easier than something buried a couple of sub-menus down that presents a wall of text.

I guess we will wait and see if the OP provides feedback.
@jerv No need to rule out others suggestions or assume what a persons capability or lack of capability is.

@blueiiznh I merely start with the most common case and adjust from there.