Laptop shuts off at random times?

It more than likely is due to heat. There is an application you can install called Speedfan. It's main purpose is to display your CPU's temperature via the thermometer placed in your CPU. Not every CPU is supported but many are so it wouldn't hurt to try it out. Honestly, anything over 60-70 degrees Celsius is going into a dangerous range. However, I've seen laptops go even higher and still sustain operation, so it all depends on the cooling the thing has. Best thing to do is to monitor the program while you do things, and try to see what the temperature is before one of these shutdowns. Best way to do this is to open up a bunch of apps (browsers, other programs) and watch until the temperature rises and it shuts down. That way you're not sitting around waiting for the thing to go under. Then, you'll know the maximum temperature your computer can take before it shuts down. So in the future you can then try to avoid reaching this temp by controlling the amount of applications you have open.