After a while, you should get used to the vibration feelings. Everyone is different though. Personally, I do some yoga and then meditate before I do astral projection and it seems to make it easier for me. Perhaps you could try some relaxation techniques before attempting it, doing so might make you more calm when you feel the vibrations. Also, the more you work with it (astral projection) the more comfortable you'll feel when attempting it.
Also, don't be disheartened if you don't achieve it the first few times you try it. I've been working with astral projection for a while now and I've only achieved what I would call partial projection. In my experiences, I've felt like my consciousness was being pulled out of my body, but my body didn't want to let go of it. That sensation eventually changed to the sensation of my torso floating up and the rest of me being stuck at the waist. I believe that would be the best way to describe it.
Just keep working with it and eventually you'll see success. It can take time for us to achieve projection or feel comfortable with leaving our physical form.