MacBook freezes after short periods of inactivity

My MacBook (Retina, 12-inch, Early 2015; n1.1 GHz Intel Core M; 8 GB 1600 MHz DDR3) was recently upgraded to High Sierra 10.13.6, after being serviced by Apple. Since the upgrade, I am experiencing frequent, maybe 2-3 times per day, freezes, where the MacBook just stop responding after short periods of inactivity. To my knowledge, my MacBook is not going to sleep. When I step away or return to my MacBook after doing something else, (such as reading, non computer type work, etc), everything is just frozen. No response from trackpad or keyboard. I have to shut down hard and start back up using power button.