Computer keeps shutting down sporadically with little pattern.

Hi all,

My mac has a weird issue where it shuts down seemingly at random, often using a web browser (happens in chrome, firefox, and safari), but also when I've been using word. I upgraded to High Sierra about a month ago and it seemed to start about a week after that.

It never crashes when plugged into a monitor and the screen is shut, but it has crashed when the screen is open and it's connected to a monitor. It happens regardless of whether it's plugged in or on battery, and I'll often open the computer and find that it shut off on it's own. I can get anywhere from 5 minutes to an hour of use without it shutting down.

It does NOT happen when I'm playing high-CPU games, using my Windows partition, or watching Netflix (it did crash on HBO Go though).

The battery is on replace soon and it does spontaneously go to sleep on occasion when it gets to ~30 to 40% remaining. Plugging it in allows me to wake it from sleep (but doesn't resolve the shutting down issue).

I'm honestly so clueless about what this is. I spoke to three support people over chat and they said they weren't really sure either.

Steps I've already taken:

• Restart with no applications open
• Reset the SMC
• Starting up in safe mode (crashed after I put it away for ~2 hours).
• Reinstalling the operating system

None of these solved the problem.

Screenshots of coconut battery and TG pro readouts. Let me know if there's more info I can provide.