Most of my lucid dreams thus far have occurred from me randomly realizing it's a dream for no apparent reason (or so I thought). I don't usually use reality checks in my dreams except to strengthen the dream after I have become lucid.

I've noticed recently, however, that most of my lucids have begun while I'm moving very fast, usually flying, but sometimes in a car or plane or something. It's not exactly a dream sign, since it isn't a very often occurrence. Nor does it stimulate some logical thought process such as "how could I be moving this quickly in real life... this must be a dream!"
It just suddenly makes me lucid.

Anybody have similar ld-inducing situations happen to them?