...As soon as I lay down to go to go I relax my whole body ( not moving anything) and start to imagine what I want to dream about...
Sometimes, I wake up 6 1/2 hours later try to do the same thing but find myself too tired to even try or focus, its like my body is not up for it...
Since you're trying to do a direct WILD rather than a dream return/WBTB and have never done one you should try for ideal circumstances.
1. It's optimal to try to WILD when the body is tired and the brain alert.
2. One needs to sleep on something comfortable- ignore the body it will relax itself if comfortable.
3. If one gives the brain permission to sleep at the same time you've made the body comfortable it will fall asleep and you'll not retain consciousness. To avoid this don't lower your eyes once you've closed them; instead look up and watch what you see with your inner eye. Don't move your eyes though -that just encourages one to think and ones goal is to get part of the brain into a theta wave state where hypnagogic images first appear.
4. Don't try to image what you'll dream about; instead incubate it. Whatever you've been concentrating on before sleep or during the day will first start to appear in ones imagination and then as HI. If you've never see HI you can use tricks to see them. Thomas Edison put a coin on this forehead and when he fell asleep it fell off waking him up. One can ask to be woke up within a few minutes of falling asleep or set an alarm for a little after the time it normally takes one to fall asleep. T. Edison did his trick sitting up and I've fallen asleep sitting up and been woke up by my headset falling off.
Once one knows ones brain is always creating HI when going asleep you'll have an easier time seeing them and would might be able to do an instant return to HI after waking up after seeing them or more likely one as one will normally see only the one running when you woke up. It's important for one to know that they really are and that one really sees them. Edison was using his HI to invent, as he had already incubated the invention while awake and HI are much more creative than the fully awake mind. Tesla also used HI to invent, but he could see them while awake and make the transition to them consciously (AKA he could WILD unlike Edison).
5. Once you've made it to HI one can play with them, try to change them or create new ones according to one's will; but one is really just waiting for the next stage of the WILD to start (AKA NREM dreams) again one can play with them or just wait for REM dreams to start.
Note: one should never experience sleep paralysis. REM muscle atonia starts normally after one has gone through both the stages of NREM dreams and dreamless Delta wave sleep. In a normal Direct WILD one slips Delta sleep and moves directly from NREM dreams to REM dreams and when REM dreams kick in they always deceive one for a moment that they're real.
Note: also that interrupting ones sleep has been demonstrated to cause sleep paralysis when one falls back asleep. People who are afraid of sleep due to having had sleep paralysis experiences and or Old hag experiences likely are falling too abruptly into REM sleep and their fear has incubated old hag experiences. Dreams and Nightmares always alternate with each other and this is true lucid dreaming too. When initiately experiencing you'll occassionally experience intense emotions that will in turn create dreams or nightmares. These emotions will be much more intense than anything you've experienced while awake and one needs to gain emotional control while lucid dreaming whether or not you have it when awake - you're a baby again when first WILDing.
Both I an others have experienced sheer terror in nightmares that lasted all night and once one is in REM sleep one is the most disassociated from ones body and will have a hard time waking up at will initially especially in any emotionally intense LD.