Random Shutting Down Even When Plugged In and On Battery

Hi there, I recently purchased a refurbished Macbook Pro Model A1278 online to replace another I lost. The model worked fine for a few months, outside of glitchy Bluetooth connections. But just over the last few days, it has begun shutting down on me at random.

A Typical Cccurrence Looks Like This:

I put on a video. The video plays for 3 minutes or so and then the device turns off. Shuts-downs occur sometimes sooner, sometimes later. It does not happen while in active use, but will as soon as I stop using (talking within 5 seconds of inactivity).

What We Know

Shuts downs occur both when on the power adapter and when on the battery. Even went so far as to unplug the battery and see if it would happen when running off purely plug power. It does.

No visible difference was seen between the shutdowns on the battery vs plugged-in.

Shut Downs occur both on the log-in screen and after logging in.

After each reboot, the chime sound is heard every time

No other devices are plugged in

Running Mac OS Cataline V 10.15.7 on a Samsung SSD

Energy saver sleep cycle is set to 2 hours, both on battery and power adapter

No hot corners present

Power

Log During Shut Downs Reads:

Timestamp                       Thread     Type        Activity             PID    TTL

2022-10-21 19:49:52.851166-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 5

2022-10-21 20:15:16.866277-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 5

2022-10-21 20:35:20.038875-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 3

2022-10-21 21:00:01.924581-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 3

2022-10-21 21:12:20.854263-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 5

2022-10-22 08:27:34.904853-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: -112

2022-10-22 08:49:05.846907-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 0

2022-10-22 08:51:52.041003-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 0

2022-10-22 09:23:12.866302-0700 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 3

2020-12-31 16:00:22.880487-0800 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 0

2020-12-31 16:06:14.860617-0800 0xab       Default     0x0                  0      0    kernel: (AppleSMC) Previous shutdown cause: 5

Fixes Tried

Running MacKeeper

Resetting SMC

Running Disk Utility First Aid

PRAM reset

Start the computer in safe mode: shut down still occurs

Possible Red Herrings:

From time to time the computer will ask me "whether I am sure I want to shut down" I hit cancel, keep working and then in a moment of inactivity, the MacBook will shut down on me.

From time to time a pink little bar will appear after powering back up

Shuts downtimes are not consistent but have gotten more sudden since starting three days ago

Happens both when hot and cold

Sometimes the device screen will go black and then wake itself up again a couple of seconds later

Happens when no applications are running

CPU's typically run in the 55-degree range

Alright, that's all I've got. Really appreciate any help. This has been quite frustrating