What do you think about me wanting to stalking someone?
Well it's not good. Why do you want to stalk someone?
I know that I'm doing something illegal, but I'm too far gone obsessing over this person
You're right stalking someone is illegal behavior and it could land you in jail. You need to keep to yourself, mind your own business and leave others alone.
What if I don't want to?
If you really like this person you shouldn't want them to feel the fear of being stalked. Wouldn't it be easier to just approach them and start a friendly conversation?