One of the most common issues I see on the internet in relation to the Surface Pro 3 is the dreaded "Stuck on the Surface screen at boot up". This can be a real problem or at a minimum a big PITA. There are many workarounds to this problem and not all of them will work for everyone. As in this case I am sure this will not work for everyone out there who has this issue also. You can however give this a try and see if it does fix your issue.
For the past 6 months I was using a Surface Pro 3 with an i5, 8GB RAM and 256GB Storage. One of the biggest issues I had with this tablet was it was sticking at the Surface screen at boot up. Many people had suggestions how to "fix" this problem but none of them were permanent or even worked every time. The fixes ranged from holding down the power button for 30 secs, holding vol up + power for 15 secs or removing the firmware and rolling back to an older version(Not sure how this was done). I found by holding the vol down + power at boot would allow me to boot into windows the first time without having to power down again. Since this key combination is used to boot from the USB drive I figured I would try and set the boot order to USB >> SSD. This has worked for me so far with one caveat, it takes 30 secs or so, did not time it, for the tablet to boot into windows. While the boot time may seem a bit lengthy, if you want to install software that requires multiple boots this will allow you to walk a way for a while. A good example is upgrading to the new version of windows 10.
IF your having an issue booting and stuck on the Surface screen give this a try, it just may work for you.