Laptop randomly shuts down while photoshop is open

A possibility could be heat build up around the processor. Most computers protect their processor from damage by measuring temperature and simply cut power to the processor if limits are exceeded. When this happens the computer just goes off without any formal shutdown or error message. You should be able to tell if your laptop is getting hot as the internal fans will get noisy and the base of the case will feel distinctly warm. You can monitor how hard the CPU is working by having Task Manager or Activity Monitor open. If the sudden shutdown happens when the machine is using 100% of the processor it's a fair bet that temperature is the cause. It would also be a good idea to check the processor fan is actually working-most machines have a utility that gives an RPM readout. Photoshop can be very CPU demanding for certain tasks and temperatures sometimes get too high even on a desktop system, laptops with much more limited air circulation are even more vulnerable. Often it is possible to set the temperatures at which fans come on or speed up via the Bios or a utility supplied with the computer. On Windows 10 you can set the operating system to underclock the processor, which also helps with heat build up but at the expense of performance. Not all laptops are made equal when it comes to dealing with heat unfortunately and it is tricky to solve.  

what exactly are you doing in ps?

perhaps you have bad memory, dust build up, etc.,