Hey, I posted this elsewhere
http://www.world-of-lucid-dreaming.com/52-ways-to-have-lucid...Also: http://www.reddit.com/r/LucidDreaming (cant believe i'm linking reddit)
I started when I was young, somebody told me it was possible so the following night I tried it - and it worked. Such is the wonder of youth :)
It comes and goes, so it does require continual 'retraining' - basically find a technique that works for you and give it your best effort. At the end of the day I suspect these 'techniques' are merely 'permission slips' allowing our brain to accept that it's possible. Either way, they can work.
The thing you have described is 'sleep paralysis' when in waking life (at least in the LD circles) - it's a very good sign, apparently you're meant to chill and just let it be. If you really needed to move (emergency), your brain would override the 'state' and allow you to (that has happened to people, the body 'unlocks' immediately).
I don't know what it means in dream life, other than it would be a good cue to remember that you have FULL control in your dream. When it happens next, remember this chat, and make yourself superman.. use your superhuman powers to break free :D Whatevvvver you like, just know that you can actually do that, because many of us do every night.
I'm no expert, since I didn't need to go through any hardships to achieve it. So perhaps there are better people for more 'concrete' advice. Good luck, it's lots of fun.