Just to preface; I do not find cold approaching appropriate and definitely do not do/condone it but;

I don't think it has anything to do with you, or looking "too easy" - It has more to do with society and the male agenda.

Maybe you're more attractive than you give yourself credit for.

You could also have a friendly/comforting demeanor about you that gives men that cold approach the confidence to do so. Maybe by flashing a smile, or making direct eye contact they think is an open invitation to speak to you.

I'm sorry you have to deal with this, I'm sure you're just trying to be yourself and act naturally, you shouldn't have to change your mannerisms to avoid being cold approached. We as a society just need to discourage these kinds of behaviors.

I had a friend once who was so tired of being cold approached that she wore a fake wedding/engagement ring. It didn't stop entirely but did severely lower the number of those kind of interactions that she had on a consistent basis.