Computer Repeatedly Restarts On Boot


On my MacPro I have multiple Startup drives. On one drive I have 10.11 gm. When I try to boot to this drive the startup gets to the gray screen with the Apple logo and then restarts over and over. It does this in safe mode. All other boot drives boot fine. This is a new HD. I did Disk repair. I reset the PRAM. All seems fine.

The only fix so far is to reinstall the OS. But after a boot or two the problem persists

Any ideas?
I've had this happen already in a couple of different situations. In my experience, seems related to using a bootable installer created using DiskmakerX, and seems to be fixed now with the latest DiskmakerX ver 5. I THINK the boot blocks on the hard drive get slightly corrupted. I could fix it by reinstalling the GM, using the installer app, and not using a bootable installer partition.

But, you say that the problem recurs after a couple of boots...

Is it only your GM boot drive that gives the problem? When you have a reboot issue again, try popping the other boot drives out as a test, so the GM is the only internal drive in your MPro. (I'm assuming that each boot drive is a separate drive, and not partitions sharing your GM boot drive?)
So I took out all the drives except 10.11. I installed the released version of 10.11. Still have the same problem
If you don't have any problems booting to the other drives, then my first thought is that there's a problem with your drive.
"New" should just remind you that you have a warranty. Sometimes you get to use the warranty, even on a new drive. New drives can fail, too...
It may pass testing, but there's one test that fails - actual use.

If I had your hard drive, I would try a "nuke'n pave", re-partition the drive, NOT a simple erase, to help assure that the partition setup is good. Reinstall, and restore whatever you need as other files and software. You lose everything that you don't have backed up, so you don't do the "wipe and restore" unless you are ready to lose everything on the drive.
This is the second new drive replacement from OWC. Note the problem only occurs with El Captain. If I put Yosemite on the Drive I do not have the problem. I don't know how to "Erase the whole
What are you using to install El Cap? (bootable USB flash drive?) What method did you use to create the bootable flash drive?
The latest DiskMakerX vers 5 does a great job, and gives you an installer that seems more stable (to me)
I would do the format while booted to Yosemite, as I haven't quite got the new Disk Utility that comes with El Cap figured out yet when one needs to control how the partitions are set.

Boot to Yosemite. Your drive that you want to use for El Cap should be in place, too. (Use a different slot this time, unless you have already tried changing to a different slot position.)
Run Disk Utility. Choose your hard drive device line (which has the hard drive information, not the partition), which is usually the first line in the list for that hard drive.
Click the Partition tab. Choose "1 Partition" from the Partition Layout dropdown. Name your hard drive, if you like. The Format should be set for Mac OS Extended (journaled). Also, double-check in Options, that the drive is set for GUID partition table.
Click Apply.
Quit Disk Utility.
Now, boot to your El Cap installer, and install OS X on your newly created partition. Should work.

Hard drive? or SSD? Exactly which drive model are you trying to use?