My trackpad has settled down now , but the computer shuts down with a debug output - in part - as follows:-
panic(cpu 3 caller 0xfffffe002d7f4c40): "busy timeout[0], (60s): 'AppleAPFSMedia'"
Debugger message: panic
Memory ID: 0x6
OS release type: User
OS version: 20D80
Kernel version: Darwin Kernel Version 20.3.0: Thu Jan 21 00:06:51 PST 2021; root:xnu-7195.81.3~1/RELEASE_ARM64_T8101
Fileset Kernelcache UUID: F78A48EC84D7C3283E7C6C67D00889A7
Kernel UUID: 9FE8C0DA-8ED0-381C-9CEC-2A779F3E1503
iBoot version: iBoot-6723.81.1
secure boot?: YES
Paniclog version: 13
KernelCache slide: 0x0000000025508000
KernelCache base: 0xfffffe002c50c000
Kernel slide: 0x000000002603c000
Kernel text base: 0xfffffe002d040000
Kernel text exec base: 0xfffffe002d108000
mach_absolute_time: 0x47c7451b066
Epoch Time: sec usec
Boot : 0x603fd3ea 0x000cc1b3
Sleep : 0x6043ed38 0x000831fc
Wake : 0x6043ef53 0x000ae1be
Calendar: 0x6043f3b3 0x00030afc
In the past this shutdown also flashed the screen Magenta as it died. Yesterday there was no flash, just black.
This has happened so often that Apple has said they shall replace my Macbook Air.
That was two weeks ago. No sign of it yet.