That weird feeling you describe is when your brain starts to slowly "disconnect" the body, as you get more and more relaxed and still in the same position. The time required to WILD depends on your practice and ability to remain calm, relaxed, and in a meditation state (as DreamHighlander said), and also on how tired, stressed, or excited you are of course... if you had lots of sleep, maybe it doesn't happen or either you lie there 1 full hour. If you're tired and are able to keep awareness without falling asleep without control, it could happen in a matter of minutes I guess...

I'm not an expert on these but on my experiences trying WILD (no success), I also feel that weird feeling, as if my hands were twisted, or not being able to tell my exact position... "where is my left arm.. up? down?"... it's like you slowly lose feeling in legs and arms. It's a good sign I guess, as long as you let your brain "go" while trying to keep awareness so it finally starts creating a dream and you just go in.