Yes, changed to that already, might have improved a bit, but not a lot, still takes at least 30sec.

Power ON the machine, tap F2 key on the startup Dell logo, it takes you to the BIOS screen. Move to "Boot" tab, Select "Boot list options" , change the option from "Legacy" to "UEFI".  Restart the machine, it should load fine to Windows. 

I've been wrestling with that same issue yesterday afternoon and this morning. The Lat 7420 became very slow to get from a shut down condition just to the initial Dell circle logo, varying between 1-2 minutes. Once the Dell logo appeared it seemed to open Windows in the normal time. Initially I thought it was related to the dock it was connected to, but it did the same thing with another dock, or just plugged into the AC adapter. I also tried setting the SSD as a priority in the UEFI list, but that made no difference. Nor did any of the other BIOS settings I tried.

After searching and finding your question on the Dell Community, it prompted me to backdate the BIOS, which had been updated to the latest (1.9.6) at some point earlier. So I downloaded BIOS version 1.8.2 from the Dell Lat 7420 support site download page and after installation (for some reason that backdate didn't fully complete until after a second restart), the time it took it took for the Dell circle logo to appear from a fresh start was much quicker.

I then downloaded the next BIOS version, 1.9.3, and installed that, and the improvement still held. Then to confirm whether the issue might be related specifically to the latest BIOS update, I downloaded and installed the latest version (1.9.6) and immediately the time from pushing the On button to Dell circle logo increased to more than a minute. So I backdated to 1.9.3 and it's back to normal. You might try backdating yours to see if that improves the situation.

So it appears to NOT be related to any of the Windows settings or configuration, and at least in my case, is an issue with the latest Latitude 7420 BIOS (1.9.6). I have no idea whether this relates to all Lat 7420's or not, but I've got 2 more to provision in the next couple days, and I'll see if one or both are affected.

BK

PS- I registered for the Dell Community specifically to reply to this issue. Hope it helps.

I have experienced the same issue on a Dell Latitude 7420 after updating the BIOS to 1.9.6.

I've confirmed the BIOS version 1.9.6 issue this morning with a brand new out of the box Lat 7320 and Lat 7420, both undocked and docked. The factory-installed BIOS was ver. 1.8.2 which was working normally. Simply updating to version 1.9.6 caused a >1 minute delay from startup to the Dell circle logo. One laptop was updated using Dell Command Update and the other from the Dell support downloads page. I've backdated to ver. 1.9.3, which seems to work fine.

Hopefully Dell monitors this type of issue and will come up with a new BIOS update.

BK

Yes, thanks people! I just downgraded to 1.9.3 and it's booting fine now. Not sure what happened to the 1.9.6 bios, maybe it is searching for boot devices a bit too long?

We appreciate your efforts in performing the troubleshooting steps. Reflashing the BIOS to the same version should have made a difference, however, please keep the system under observation and do reach out to us in case you need any assistance. 

Thanks so much for this, I also updated to 1.9.6 on a new machine and thought this thing was broken as I had not had much cold boot experience prior to updating (I.E I didn't pay attention as I was mainly running updates).

Thought I was going crazy with how long cold boot was taking... easily 30+ sec. I have now downgraded to 1.9.3 as per your suggestion and it's so much faster it's crazy, under 10s and I'm into Windows.

Dell needs to look into this! 

Thanks again!

I have the same issue. Upgraded from the stock BIOS to 1.9.6 and notice about 2 to 3 minutes boot lag. Please fix this issue ASAP.

My new latitude 7420 is too wery slow boot, and slow working. I don't undertand why. I just change it from 7390 and for some reason 7420 it's much sower. the same I7 and 16Gb RAM
I even have to wait for the letters to appear after typing. Maybe you can advise something