This happens here every now and then on a ThinkPad T470 with the latest BIOS installed and an internal Intel Wireless 8265 / 8275 adapter:

$ grep NMI_INTERRUPT_UMAC_FATAL  /var/log/system.log | tail -5
Dec 30 15:19:41 horus kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    
Dec 30 15:19:42 horus kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    
Dec 31 17:51:17 horus kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    
Dec 31 17:51:21 horus kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    
Jan  2 13:08:12 horus kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    

Full example:

kernel: iwlwifi 0000:04:00.0: Microcode SW error detected.  Restarting 0x2000000.
kernel: iwlwifi 0000:04:00.0: Start IWL Error Log Dump:
kernel: iwlwifi 0000:04:00.0: Transport status: 0x0000004A, valid: 6
kernel: iwlwifi 0000:04:00.0: Loaded firmware version: 36.ca7b901d.0 8265-36.ucode
kernel: iwlwifi 0000:04:00.0: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL    
kernel: iwlwifi 0000:04:00.0: 0x00000083 | trm_hw_status0
kernel: iwlwifi 0000:04:00.0: 0x00000000 | trm_hw_status1
kernel: iwlwifi 0000:04:00.0: 0x00024A8C | branchlink2
kernel: iwlwifi 0000:04:00.0: 0x0003AC1E | interruptlink1
kernel: iwlwifi 0000:04:00.0: 0x00004DD2 | interruptlink2
kernel: iwlwifi 0000:04:00.0: 0x00000000 | data1
kernel: iwlwifi 0000:04:00.0: 0x00001000 | data2
kernel: iwlwifi 0000:04:00.0: 0x03830000 | data3
kernel: iwlwifi 0000:04:00.0: 0x63810560 | beacon time
kernel: iwlwifi 0000:04:00.0: 0xFD6F9A71 | tsf low
kernel: iwlwifi 0000:04:00.0: 0x00000055 | tsf hi
kernel: iwlwifi 0000:04:00.0: 0x00000000 | time gp1
kernel: iwlwifi 0000:04:00.0: 0x26462734 | time gp2
kernel: iwlwifi 0000:04:00.0: 0x00000001 | uCode revision type
kernel: iwlwifi 0000:04:00.0: 0x00000024 | uCode version major
kernel: iwlwifi 0000:04:00.0: 0xCA7B901D | uCode version minor
kernel: iwlwifi 0000:04:00.0: 0x00000230 | hw version
kernel: iwlwifi 0000:04:00.0: 0x00C89000 | board version
kernel: iwlwifi 0000:04:00.0: 0x0A4F001C | hcmd
kernel: iwlwifi 0000:04:00.0: 0x26FE3002 | isr0
kernel: iwlwifi 0000:04:00.0: 0x11800000 | isr1
kernel: iwlwifi 0000:04:00.0: 0x0800181A | isr2
kernel: iwlwifi 0000:04:00.0: 0x40412180 | isr3
kernel: iwlwifi 0000:04:00.0: 0x00000000 | isr4
kernel: iwlwifi 0000:04:00.0: 0x0A47001C | last cmd Id
kernel: iwlwifi 0000:04:00.0: 0x00000000 | wait_event
kernel: iwlwifi 0000:04:00.0: 0x00004A88 | l2p_control
kernel: iwlwifi 0000:04:00.0: 0x00019C24 | l2p_duration
kernel: iwlwifi 0000:04:00.0: 0x0000003F | l2p_mhvalid
kernel: iwlwifi 0000:04:00.0: 0x000000EF | l2p_addr_match
kernel: iwlwifi 0000:04:00.0: 0x0000001D | lmpm_pmg_sel
kernel: iwlwifi 0000:04:00.0: 0x10032209 | timestamp
kernel: iwlwifi 0000:04:00.0: 0x00002030 | flow_handler
kernel: iwlwifi 0000:04:00.0: Start IWL Error Log Dump:
kernel: iwlwifi 0000:04:00.0: Transport status: 0x0000004A, valid: 7
kernel: iwlwifi 0000:04:00.0: 0x00000067 | ADVANCED_SYSASSERT
kernel: iwlwifi 0000:04:00.0: 0x00000000 | umac branchlink1
kernel: iwlwifi 0000:04:00.0: 0xC008694C | umac branchlink2
kernel: iwlwifi 0000:04:00.0: 0xC0083B0C | umac interruptlink1
kernel: iwlwifi 0000:04:00.0: 0xC0083B0C | umac interruptlink2
kernel: iwlwifi 0000:04:00.0: 0x00004000 | umac data1
kernel: iwlwifi 0000:04:00.0: 0xC0083B0C | umac data2
kernel: iwlwifi 0000:04:00.0: 0xDEADBEEF | umac data3
kernel: iwlwifi 0000:04:00.0: 0x00000024 | umac major
kernel: iwlwifi 0000:04:00.0: 0xCA7B901D | umac minor
kernel: iwlwifi 0000:04:00.0: 0xC088628C | frame pointer
kernel: iwlwifi 0000:04:00.0: 0xC088628C | stack pointer
kernel: iwlwifi 0000:04:00.0: 0x0086014E | last host cmd
kernel: iwlwifi 0000:04:00.0: 0x00000000 | isr status reg
kernel: iwlwifi 0000:04:00.0: IML/ROM dump:
kernel: iwlwifi 0000:04:00.0: 0x00000000 | IML/ROM error/state
kernel: iwlwifi 0000:04:00.0: 0x00000003 | IML/ROM data1
kernel: iwlwifi 0000:04:00.0: Fseq Registers:
kernel: iwlwifi 0000:04:00.0: 0x254FF6BE | FSEQ_ERROR_CODE
kernel: iwlwifi 0000:04:00.0: 0xEB4D862A | FSEQ_TOP_INIT_VERSION
kernel: iwlwifi 0000:04:00.0: 0x94078394 | FSEQ_CNVIO_INIT_VERSION
kernel: iwlwifi 0000:04:00.0: 0x0000A10B | FSEQ_OTP_VERSION
kernel: iwlwifi 0000:04:00.0: 0x23B1050F | FSEQ_TOP_CONTENT_VERSION
kernel: iwlwifi 0000:04:00.0: 0x2DFF3649 | FSEQ_ALIVE_TOKEN
kernel: iwlwifi 0000:04:00.0: 0xC953F0BA | FSEQ_CNVI_ID
kernel: iwlwifi 0000:04:00.0: 0x02B66AEC | FSEQ_CNVR_ID
kernel: iwlwifi 0000:04:00.0: 0x00000010 | CNVI_AUX_MISC_CHIP
kernel: iwlwifi 0000:04:00.0: 0x0BADCAFE | CNVR_AUX_MISC_CHIP
kernel: iwlwifi 0000:04:00.0: 0x0BADCAFE | CNVR_SCU_SD_REGS_SD_REG_DIG_DCDC_VTRIM
kernel: iwlwifi 0000:04:00.0: 0x0BADCAFE | CNVR_SCU_SD_REGS_SD_REG_ACTIVE_VDIG_MIRROR
kernel: iwlwifi 0000:04:00.0: Collecting data: trigger 2 fired.
kernel: ieee80211 phy0: Hardware restart was requested
[...]


$ lspci -s 04:00.0 -v
04:00.0 Network controller: Intel Corporation Wireless 8265 / 8275 (rev 78)
        Subsystem: Intel Corporation Dual Band Wireless-AC 8265
        Flags: bus master, fast devsel, latency 0, IRQ 136
        Memory at ec100000 (64-bit, non-prefetchable) [size=8K]
        Capabilities: [c8] Power Management version 3
        Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [40] Express Endpoint, MSI 00
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [140] Device Serial Number e4-70-b8-ff-ff-3f-cc-8f
        Capabilities: [14c] Latency Tolerance Reporting
        Capabilities: [154] L1 PM Substates
        Kernel driver in use: iwlwifi
        Kernel modules: iwlwifi