System:

CPU
Intel Core i7-8700 @ 3.2 GHz 8th Generation

Memory
Micron Technology MTA8ATF1G64AZ-2G6E1 x 16GB
DDR4 2666 MT/s (PC4-21300) CL19 SR Unbuffered DIMM 288pin
DDR4 SDRAM Dual 2666MHz 19-19-19-43

Storage
Samsung SSD 980 NvMe M.2 MZ-V8V500B/IT 

Monitor
Dell E2216H

BIOS
OptiPlex_3060_1.32.0.exe

OS
Windows 11 Pro 25H2
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Problems:

1) Dell Logo flashes twice on boot (did for ages)
2) Windows sign in flashes twice on boot (did for ages)
3) Mouse cursor jumps up when scrolling downward
   (from about two months ago)

Done so far:

1) Swapped mouse and changed connection to different USB2.0 port
2) Ran full Dell Diagnostics
3) Ran Passmark Memtest86
4) Did clean install of Windows 11
5) Tried various Internet suggestions for supposedly fixing
   mouse scrolling probem
6) Flashed Dell BIOS
7) Etc., Etc.

No errors found and nothing improved.

Can anyone help, please?

Thanks for your time.