What is this flash phenomena i keep seeing?

[Taylor G]

A few years ago i was at my grandparents beach house with my brother and a couple friends. We're in the bedroom in our beds and it was about 3 or 4 am or so. The lights were off and we were talking. Suddenly a flash of light filled the whole room. It was so quick i didn't even process the flash until after it happened. My brother and I were the only ones that saw it. I figure our friends had blinked at the time it happened. This light was also silent so i don't think it was an electrical thing. I figured some weirdo must have taken a picture of the room through the window since it was on the first floor. And then the other night in my dorm room it was about the same time of night and my roommates were asleep and i saw the same flash. I was on my computer and the room lit up. We're on the second floor with our blinds shut. I've been trying to figure out what this is. if anyone knows what this is or has any information that would be great. Thanks!