I was using my 2019 MacBook Pro this past Tuesday for most of the day, on battery. At the end of the day, I closed the lid and put it in my backpack to head to a friend’s house. This morning (Thursday), I pulled the MBP out of my backpack, opened the lid and the MBP started booting, as opposed to just offering me the option to sign-in. I’d had a few documents open when I closed the lid Tuesday, and those were lost, due to the unexpected shutdown. The battery was at 41% when I opened the lid.
Any ideas as to what happened to cause the MBP to shutdown?
Don’t know for sure but my iMac starts to act wonky if it hasn’t been restarted around the 3-week mark.
My iMac has run for months with no problems. Could be some software you’re using.
My MBP occasionally reboots when it should have slept. Could the battery have been low when you closed your laptop, then you connected to a charger later before turning it on even later?
That was my immediate thought as well, as I’ve experienced this in the past with work MBPs. I’d close the lid, and when I’d return to the MBP, I’d find the battery completely dead. That wasn’t the case in this instance, as the battery was at 41% after it finished booting, and dumped me into the Finder.
No, even with 40Gb RAM I end up using apps with memory leaks, and it eventually takes its toll; a simple restart usually is all I need. Happened again a couple of weeks ago.
My current uptime is 7 days, and I’ll do another restart in another week.
That would be the “some software you’re using” 
We’re not disagreeing. I was trying to help the OP.
Memory leaks are always a possibility.
Have looked at the console logs? There might be an entry there that could help you find the cause?
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My older MBP got into the mode – when not plugged in – where it would boot and display a good battery percentage, and then a few seconds later shut down and display the red 0% battery icon. When I plugged it in and booted it reported 1 or 2% battery. After a few weeks of this occurring off and on, that’s when the “Service Battery” warning started appearing.
Short story: the MBP appeared to lose the ability to accurately gauge battery power and would shut down. Often shutting down while the lid was closed.
