I have the same problem, almost a week back my iMac was unable to boot, with the wheel spinning continuousely after i type my user password, i did a full folrmat of the harddisk and installed a fresh copy.\
it worked fine for over a week, since 2 days bacj it styarted ubruptly shutting down without any warning, just blink and its off
when it reboots i get the below error log
Sleep Wake failure in EFI
Failure code:: 0x00000000 0x0000001f
Please IGNORE the below stackshot
================================================================
Date/Time: 2021-03-31 12:04:59.953 +0300
OS Version: ??? ??? (Build ???)
Architecture: x86_64
Report Version: 32
Data Source: Stackshots
Shared Cache: 52762DF1-0E55-3F8B-9588-8169E6D0EB95 slid base address 0x7fff20236000, slide 0x236000
Event: Sleep Wake Failure
Duration: 0.00s
Steps: 1
Time Awake Since Boot: 27s
Process: swd [320]
Architecture: x86_64
Footprint: 400 KB
Time Since Fork: 4s
Num samples: 1 (1)
Thread 0x899 1 sample (1) priority 4 (base 4)
<thread QoS background (requested background), thread darwinbg, process darwinbg, IO tier 2>
1 start + 1 (libdyld.dylib + 87585) [0x7fff20562621] 1
1 ??? [0x108167454] 1
1 ??? [0x1081671e8] 1
1 __stack_snapshot_with_config + 10 (libsystem_kernel.dylib + 143386) [0x7fff2053501a] 1
*1 ??? [0xffffff80002601f6] 1
*1 ??? [0xffffff80009698cb] 1
*1 ??? [0xffffff80008733c1] 1
*1 ??? [0xffffff80002831c9] 1
*1 ??? [0xffffff80002ba3ed] (running) 1
Binary Images:
0x7fff20512000 - 0x7fff20540fff libsystem_kernel.dylib (7195.81.3) <AB413518-ECDE-3F04-A61C-278D3CF43076> /usr/lib/system/libsystem_kernel.dylib
0x7fff2054d000 - 0x7fff20587fff libdyld.dylib (832.7.3) <4641E48F-75B5-3CC7-8263-47BF79F15394> /usr/lib/system/libdyld.dylib
appreciate your support