MacBook Air turning off after being idle at login window

Hi everyone,

I have an Apple MacBook Air "Core i5" 13" 2017 model running OSX 10.14. I have encountered an issue with the machine that occurs when I have the login window on the display for some time, around five minutes or so, then the machine powers off.

I spoke to apple care support and they recommended me to check energy saving settings and reset the SMC and NVRAM, I also checked First Aid and tried safe mode and it still shuts off after being at the login window for around five minutes. I followed all those steps with no luck. I am not sure where the issue is unfortunately. Is this a power issue? Or a software issue? Please point me in the right direction.

Thanks,

Nick