I was just using my computer and a small window opened and then closed very quickly. I got a quick glimpse of it. It wasn't a command prompt but I have seen those do the same thing. I only had a few tabs open. A forum I frequent and youtube.
It all depends on what you were doing and you didn't say. A few things are compressed and can open a DOS mode window to decompress. If you're talking about Chrome suddenly closing, that is abnormal, but frankly it's not clear what you're talking about.