Working in Photoshop leads to computer restart (Mac)

In modern computers, applications are insulated from the operating system and cannot cause this. It's not possible.

An application can crash or freeze, but not take down or restart the whole operating system.

Drivers can, however, they operate on a lower level. A buggy driver could do this, e.g. the video driver. Another common cause is failing hardware components. The very first thing to check is if some part of your machine may be overheating. Check for excessive dust accumulation on the fans.

Photoshop may well trigger something like this, because of what it asks the other components to do, but it cannot be the cause.

Please ensure your computer meets or exceeds the minimum system requirements to run Creative Cloud + OS + all other apps you use. Check each one.
- https://helpx.adobe.com/creative-cloud/system-requirements.html

Pay particular attention to Photoshop's new GPU requirements. See links below.
- https://helpx.adobe.com/photoshop/system-requirements.html
- https://helpx.adobe.com/photoshop/kb/photoshop-cc-gpu-card-faq.html

Try Resetting Preferences.

https://helpx.adobe.com/photoshop/using/preferences.html