BIOS 1.12.2 appears to be fixing the issue for some. If you have not installed it, do so and retest. BIOS 1.13.0 addressed a different issue. Latitude 7320/7420/7520 BIOS 1.12.2, November 24, 2021Fixes & Enhancements- Fixed the issue where the system cannot resume from Modern Standby using the proximity sensor.- Fixed the issue where the system prompts for a password after rebooting the system when Reboot Bypass is enabled in BIOS Setup menu.- Fixed the issue where the system does not respond after disconnecting the Dell W19TBS dock when Enable Thunderbolt Boot Support option is enabled in BIOS. Latitude 7320/7420/7520 BIOS 1.13.0, December 8, 2021Fixes & Enhancements- Improved the system stability for Hynix 8G/16G memory.
Just checking to see if anyone has similar issue. We've recently bought 5 new latitude 7420 laptop. running 1 unit through command update to get all the latest drivers & patches I noticed it takes almost 2 min to get Dell logo to show on the power up screen. Wasn't aware of the issue at the time, until  noticed the same issue when I go through setting up the second unit. Both units are running BIOS version 1.9.6. Then I fired up the 3rd unit just to confirm, only updating BIOS this time and nothing else, same issues happened. Dropped BIOS version down to 1.9.3 and boot delay issue disappears. Has anyone had similar issue?  
Latitude 7420 BIOS update to 1.9.6 cause system boot delay