I get these too. They're not urges--in fact they usually repulse or frighten me--but intrusive and often graphic flashes. They're a well established common symptom of OCD (my NPD/ego defenses aside, my OCD manifestations are typically habitual rechecking, and these intrusive images of the non-sequitur variety).

Obviously being as disturbing as they are, many tend to irrationally imagine these are some manifestation of something worse, or signifying some loss of control. This is not the case, and should be readily debunked by our understanding of OCD.

I'm starting to feel like an unpaid shill for various authors who don't know I exist, but I generally swear by all of the books I've recommended. I don't know if you've heard of or read Brain Lock: Free Yourself from Obsessive-Compulsive Behavior by Jeffrey Schwartz M.D., but it came up as Amazon's most popular choice for self-help in this arena several years ago. I do recommend this book.

Since anxiety usually precipitates poor processing of these thoughts (e.g. "I'm a bad person," "I'm a monster," "who thinks like this?," "am I coming unglued?"), it activates the amygdala and further exacerbates the OCD, which causes more anxiety, which of course gives us the vicious cycle. That book gives you a series of processing steps for OCD thoughts of all types. The more you learn how to process them, the less severe and repetitive they become.

I find myself returning to this book (not because of compulsions to reread things!) every few years anytime I get away from proper processing.