I've had this happen a few times, but not very often. I can't say if your subconscious is purposefully trying to get you lucid, but if you believe it is, this belief is probably going to come true. I mean, intention is key in getting lucid, so if you go to bed every night thinking your subconscious will help you get lucid, it probably will. I don't know for sure if it would work, but somehow it should have the same effect as if you were stating a regular mantra.