Because the Mac is unexpectedly restarting, first install any available macOS updates if available.
Then disconnect the second display, dock, hub, adapters, and other unnecessary peripherals and use the Mac for roughly the amount of time it normally takes for a restart to occur.
Apple recommends disconnecting peripherals when investigating unexpected restarts and reconnecting them individually if the problem stops. Apple — If your Mac restarted because of a problem
If the Mac remains stable, reconnect the external display directly to the MacBook Pro, without a dock or hub.
Test Thunderbolt/USB-C and HDMI separately, preferably with a different known-good cable.
If possible, also test the Mac with a different external display.
Comparing the original display with another display can help determine whether the behaviour follows the display or remains with the Mac. Apple — If your external display is dark or low resolution
Verify that the display is operating at a resolution and refresh rate supported by the MacBook Pro and the display.
Also check the display manufacturer's support site for available firmware updates. Apple — How many displays can be connected to MacBook Pro
Next, test the same display configuration in Safe Mode.
If the behaviour changes, that provides information about software loaded during a normal startup, but does not by itself establish the cause.
A temporary user account is another useful isolation test.
Use the same external-display configuration and determine whether the unexpected restarts also occur there.
This can help distinguish behaviour associated with your normal user environment from behaviour that occurs more generally.
In your normal user account, you can also run EtreCheck and save its report.
It can provide an inventory of third-party software, extensions, login items, and other system components that may be relevant. Its report should be used as diagnostic information rather than as evidence that any particular item is causing the crashes.
After another unexpected restart, save the diagnostic or panic report macOS provides. If you provide the report, it can be examined for specific references to graphics, the external display, Thunderbolt, WindowServer, or other components. This provides substantially better evidence than trying to determine the cause from the symptoms alone.
If the restarts continue even with the external devices disconnected, run Apple Diagnostics with unnecessary peripherals disconnected.
On an Apple-silicon Mac, shut down, press and hold the power button until the startup options appear, then hold Command-D. Apple — Use Apple Diagnostics to test your Mac
I would complete these tests before deciding whether to revert macOS.
They can establish whether the behaviour is associated with the external-display setup, a particular display or connection, software loaded during startup, your normal user environment, or a possible hardware issue.
For your presentations, if the Mac proves stable without the external display, using that configuration temporarily may be the most practical way to avoid the unexpected restarts.
If the display is required, use the simplest configuration while testing: connect the MacBook Pro directly to the display with one cable and without a dock, hub, or adapter.
