Q: iMac random freezes and reboot after upgrade

Hi. I work in an iMac 21.5 late 2013, 8GB, 1TB HDD.

This week I send it to a technical assistance to upgrade it to 16GB and a 500GB SSD.

This was a great upgrade, with a significantly boost in speed and performance, but now I have a problem: the machine randomly freezes and reboot. I couldn't detect what is causing this. Today I formatted it with a fresh install but the problem persists.

My most common programs in use are: Adobe Photoshop CC, Illustrator, Google Chrome (lots of tabs), and Slack.

Here is my Mac specs:

Thanks for the help.