Can't tell from your description but it's possible we both have similar issues. On boot-up, my screen goes dark three (3) times. There are no issues associated with it, in that the phone works find once I hit the power button to jostle the phone into its normal lock screen. Don't know what started it, but I think it began a year ago - maybe when there was an OS update of sorts.
Again there have been no issues other than that mild inconvenience (at least for me) so I think your phone will keep working well, once fully booted.
I hope what I said will make you feel a little better. We expect a lot from a $700 phone including perfection. But we have to settle for 95% - not bad - 95% of it works perfectly in my opinion. 