A few days ago, I looked again at the “Fast Startup” settings and found it ON. Now I think that I turned off the “Fast Startup” before (not after) I reinstalled Windows. I turned it off again. The computer is powering up normally ever since. I hope that is all I needed. I accept this as the solution.   Thank you all for your suggestions.
I have a four-year old Dell XPS 8910 computer with the latest Windows 10 Home version (21H1) and BIOS 1.1.12. Recently, the coin cell battery was replaced with a brand new, and a cleaning of the internals was performed. For the last several months, almost always, when I try to start my XPS 8910 computer, after I touch the power button, the keyboard and mouse lights blink for a couple of seconds, and then go out. For the next 3 or 4 minutes, the screen remains black or only shows the Dell logo. Windows 10 is not booting because I don’t see a circle of rotating white points. Then, the computer shuts itself off. After I push the power button for the second time, the boot is successful. At other times the black screen lasts 10 minutes, or more. If I push hard on the power button, sometimes the computer shuts off, but other times I have to disconnect and reconnect the power cord. I reinstalled Windows 10 (keeping my files, and without a clean install, full disk format), but the problem persists. I turned off the “Fast Startup”, but the problem persists. No solution after a chkdsk. No solution after doing a Windows files system check (DISM.exe) and the SFC scannow. I have Norton 360 and Malware-bytes, but they do not report malware. No solution after opening the computer, doing a cleanup and putting a brand new cell coin battery. I appreciate any suggestions.
XPS 8910, problems when powering up