Original post by: Toronto Tim ,
I have been experiencing these sudden shutdowns on my mid-2014 MacBook Pro 15" Retina. I've tried the SMC and PRAM resets and nothing was helping. So I got on a support chat with Apple and their fix seems to have WORKED!!! System Preferences > Users and Profiles Under your Profile, go to Login items and look for any entries with warning symbols against them. I had 4 different ones (Skype for Business was one). I removed those entries from the Login items, in some cases removed the applications altogether and NO PROBLEMS SINCE! I was experiencing sudden shutdowns multiple times daily. It happened during the support chat with Apple. They mentioned possible Kernel panics as well, but this seems to have resolved my problem. If you're at your wits end check this. If you're not sure, reinstall macOS from scratch. Glad my problem appears to have been purely software.