Q: El Capitan cannot find startup drive without holding down 'X' key

Thank you Grant.  I mentioned Startup in System Preferences to point out there was no other system other than El Capitan. Yes it always starts back up on restart and the drive I am aiming for is always the one showing being selected. I even went as far to unlock the lock, re-select the same system, and then authenticate the change three times even though it was not a change.  On restart it came right back to the right drive.

My issue and question comes into play each time after I have a total shutdown—once a day, every day—to save energy.  It is the morning after (or just now) as I shut it down totally after the restart you suggested.  Without holding down the 'X' key I get a white screen—no Apple logo, no startup. If I do not hold down 'X' soon enough, I must turn it off with the start button, wait a few seconds and start again. And then it works:  I get the chime, I get a temporary white screen and then the Apple logo, etc.

No I have not.

Recently, before I installed El Capitan I had Yosemite. There were earlier systems on my drives, like Snow Leopard and earlier. I made the mistake of stepping back too far to one of them and that system could not see Yosemite so I upgraded to El Capitan.

I did just that and there is no change in requiring me to hold down the 'X' key to start.  Yes it is wonky, but my Mac does work and I am thankful for that.

So nothing was gained by installing the 10.11.6 combo, but I did not stop there.  I had always asked locally if anyone thought the order of the drives in the four bays would play any part in my wonky problem. I put my 2TB drive in bay 1 and what was in bay 1 went to bay 3. So now the startup partition was the beginning of the chain.  And then I zapped the pram—which I had done before but to no avail.

Now from a total shutdown to startup there is no white screen more than a few seconds before the Apple logo and startup.

Thanks for sticking with me on my wonky problem.

No, I mean the "X" key. It is the first item in an Apple Service & Support document for Mac OS X keyboard shortcuts. I downloaded and printed it years ago. Category one is the Startup Keystroke to force Mac OS X startup.

I said years ago because this is an early 2008 Mac Pro desktop. The link above in your reply lists the "X" key as item 13, whereas on my list it is item 1.

Why is there an edited comment in your reply? You don't have to answer.

I understand. I went with the list I had. Had it not worked the first time I would have gone on to find something else.

Thanks.