MacBook Air randomly switching off

Here is information on safe mode startup:

Start up your Mac in safe mode - Apple Support

This eliminates add ons so the computer boots into a most basic state to check if add on software is causing an issue.

I am still running Sonoma with my MacBook Air.

When you close the clam shell (screen) the Macbook Air is being sent into a sleep mode.

If you immediately open the clam shell, I can see how you are now trying to interrupt sleep mode and the processor gets confused - causing a restart.

If you don't immediately open the clam shell, you wait a second or two, how does it behave - does it wake from sleep properly?

There is no automatic test with Safe mode.

Safe mode allows you to operate the mac without added on software. Try diagnosing it yourself and see if when you close and then immediately open the screen to see if the same happens.

There is also an Apple Hardware Diagnostics program that you can run. It is not automatic. Here are the instructions:

Use Apple Diagnostics to test your Mac - Apple Support

If this is all too much for you to handle, take it to the apple store and have an apple genius look at and run hardware tests. They charge a nominal fee for running diagnostics to determine if something is wrong.

Otherwise, you can stop immediately opening the screen after closure and perhaps just live with the issue if it is not effecting the normal operation of the computer.

You just restart the computer to exit safe mode. You want to see if safe mode fixes things. If so, there is some added software causing problems. It rules out the hardware causing the issue.