I appreciate your inputs, @6x12. Thank you.
Digging around I realised that my system was locked in a high performance mode. That explains why also I have had a lot of issues with annoying fan noise, and the high temperatures. I tried out the Tuxedo Control Center. Several features are missing on Manjaro, but I can alter the profile / power mode through that tool.
This was the previous active profile:
Now, I am trying out a predefined mode named “Cool and breezy”:
The notebook has been running, doing different tasks, for five hours, and the temperature now looks like this:
$ sensors
coretemp-isa-0000
Adapter: ISA adapter
Package id 0: +44.0°C (high = +82.0°C, crit = +100.0°C)
Core 0: +42.0°C (high = +82.0°C, crit = +100.0°C)
Core 1: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 2: +42.0°C (high = +82.0°C, crit = +100.0°C)
Core 3: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 4: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 5: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 6: +42.0°C (high = +82.0°C, crit = +100.0°C)
Core 7: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 8: +43.0°C (high = +82.0°C, crit = +100.0°C)
Core 9: +42.0°C (high = +82.0°C, crit = +100.0°C)
pch_cometlake-virtual-0
Adapter: Virtual device
temp1: +65.0°C
nvme-pci-4300
Adapter: PCI adapter
Composite: +49.9°C (low = -273.1°C, high = +81.8°C)
(crit = +84.8°C)
Sensor 1: +49.9°C (low = -273.1°C, high = +65261.8°C)
Sensor 2: +49.9°C (low = -273.1°C, high = +65261.8°C)
BAT0-acpi-0
Adapter: ACPI interface
in0: 16.27 V
curr1: 0.00 A
iwlwifi_1-virtual-0
Adapter: Virtual device
temp1: +55.0°C
nvme-pci-0700
Adapter: PCI adapter
Composite: +51.9°C (low = -273.1°C, high = +84.8°C)
(crit = +84.8°C)
Sensor 1: +51.9°C (low = -273.1°C, high = +65261.8°C)
Sensor 2: +46.9°C (low = -273.1°C, high = +65261.8°C)
nvme-pci-0600
Adapter: PCI adapter
Composite: +55.9°C (low = -273.1°C, high = +84.8°C)
(crit = +84.8°C)
Sensor 1: +55.9°C (low = -273.1°C, high = +65261.8°C)
Sensor 2: +46.9°C (low = -273.1°C, high = +65261.8°C)
acpitz-acpi-0
Adapter: ACPI interface
temp1: +45.0°C
I will test this profile for a few days, to see if the system still shuts down on its own. If it does not help I will keep checking out the BIOS options, and look at powertop.