My first LD was less than 10 seconds lol. I became spontaneously lucid in an university and I tried to walk but I just couldn't, it was like I was moving through invisible mercury lol And then I just woke up (really woke up, not a False Awakening).

It was very short, but just the sensation of being aware in a dream was amazing, it lasted for weeks, and that got me very motivated to keep trying.