Wont boot fully till FROM Safe Mode !

How can I diagnose what prevents normal booting, if success requires rebooting from Safe Mode ? My PC's species are correctly listed in System Specs.

You seem to have misunderstood the question. I was asking how the booting impediment can be diagnosed. The 'problem' has already been solved temporarily, but I still have no idea what is going wrong.

sfc /scannow found no integrity violations. I routinely monitor what starts up as shown in Task Manager and Autoruns. Could you name Bios Diagnostic program for me ? HDSentinel gave a most contradictory assessment of the HDD (SSD). The current system disk is a clone of another SSD that was continuously failing to boot, until I reseated the signal and power connectors. Since I've used the clone (on different SATA leads) there have been very few failures, yet HDSentinel 'said' that the current system had a bad sector and experienced 1200 problems between communication of the disk and the host - something that could be expected from the source of the clone; yet it gives that clone-source a totally clean bill of health !

Problems related to slow boot can be found by safe mode and clean boot.
There are additional tools / methods.

Problems related to failure to boot that has been fixed may or may not appear in log files.

Problems related to failure to boot that has not yet been fixed may or may not appear during the troubleshooting steps.

Routine hardware monitoring can also be performed.

No data recovery is involved here. So I am saved .

Slow boot need not necessarily imply a problem with the system disk only. Any failing disk where bad sectors have started showing up - be it an internal drive or external plugged in drive can cause the slow boot. And the OP has two seondaray drives too.

He should disconnect those two drives, unplug any other external storage devices and then check his system drive; a) With the present clone as the system drive and b) with the clone source as the system drive. Does the system boot "normally" with both these twins? What does Hard Disk Sentinel say about these two drives when used as system drive - as checked in the system? Does his system boot "normally" as per his perception?

If OP's system does not boot normally with either of these, then he should do a clean install on a new or known good drive and check whether the system boots normally.

Once "normal boot" is restored, he should test the other two internal drives connecting one at a time.

This way the OP can diagnose which of the disk is causing the slow boot - if a failing disk is causing the problem.

You appear to be giving a remedy to a slow boot - slow booting was involved but was not my concern. The fact that I could boot normally only after passing through Safe Mode is my concern. Apparently Safe Mode rectifies something - it would be useful to know what that is, so that it can be corrected/eliminated.

So your question is : After booting once into safe mode, normal boot is restored. So what did safe mode correct?

My answer: I do not know . I haven't heard of such an eventuality. May be the other experts have an answer. .