My SP3 i7/256 has been doing the same since the last firmware update 19/5/2015 which I installed on 24/5/2015. I get two white flashes every time I wake up the device or switch it on etc. Was fine before the update. Looks like Microsoft has stuffed something up here.
No not only i7, I have an i5, 128gb and it is also doing it.
...mine too i5/8GB/256, since the last update. Also, mine is running warmer and the fan is coming on more frequently since the last update.
My white flash started after the last update as well.