macbook pro hangs on startup

This a MacBook Pro 17" Early 2011 2.2ghz upgraded with a Intel SSD

It will not start/boot. It gets about half way on the progress bar and either gets a squiggly band 1 1/2 inched down the screen and then blinks and gets stuck on a gray screen. Sometimes it blinks to black for a second and goes to the gray screen.

Here what I've tried.

1. Reset the NVRAM

2. Reset the SMC

3. Tried to boot to a Sierra usb install flash drive - hangs on gray screen

4. Tried to boot to a usb hard drive with Sierra installed - hangs on gray screen

5. Plugged in a network cable and restarted holding down "d" - it ran diagnostics and passed

6. Took the SSD out, put it I a usb drive caddy and ran disk tools from another MacBook pro. No errors found.

7. With no ssd or hdd in the MacBook Pro, tried to boot to flash drive install and usb hard drive with Sierra. - hangs on gray screen.

8. I removed the RAM and swapped positions and re-seated.

I can hold down option and it will boot to the menu/screen that allow you to choose the start-up disc.

As I was writing this post, on a whim I restarted holding down the option key like I've done all night. No usb drives connected. This time I clicked the only drive showing, the Macintosh HD, and the thing booted. It doesn't make sense. If this was all that was wrong, why would it not boot to the usb drives?

Any insight would be appreciated.

Marshall