When he/she is trying to bite? Is it when you are trying to pick up or during holing. If it is when you are trying to pick him/her up it may be the angle of approach. They are afraid of things coming from above, so it is better to put your hand under them when they are babies or they think that you are a bird trying to eat them. LOL Baby beardies are very quick and jumpy. Don't worry about the bite though, even when they are older it doesn't hurt. Scorch has only bitten me once and it was an accident. I put my finger in her mouth to try and fish out a piece of bark that she had gotten a hold of (naughty girl) and chomp. It is just a pinch, doesn't hurt at all.
I started leash training Scorch when she was about 5 months old in February. Prepare for resistance the first week or so, patience is key. Scorch still is not crazy about wearing the leash for long periods of time, but it is very easy to get it on her because she knows that if she wants to go for a picnic or get time outside in the grass she will have to put up with it. If you associate the leash with something that your baby likes, ex outside time or a particular snack food, then the routine of getting the leash on and keeping it on will probably go better for you. You may want to try the beardie buritto trick to calm your baby and get them used to you before you try leash training. If you try wrapping your little guy in a blanky and snuggling before bedtime or early in the morning when they are cold, they will get used to your smell and it helps with trust too. Good luck!!