Is it normal to get turned on by this?

No problem with that. You like to be dominated. First it's being pinned down. Once you have found a good Master you can trust you can go to the next few levels in steps. Using restraining clothing that limits your movements, then actually being tied down (Rope, Handcuffs, etc), and from then what ever you both enjoy. Be careful though, take it easy so not to get hurt.