How Do I Tell my Wife our Sex Life Sucks?

I am married and my wife and I have what I would call a good marriage. However, I feel our sex life could do with a little shake-up. For instance, I would like it to be adventurous especially in terms of sex positions and unpredictable venues. But how do I tell my wife I’m not satisfied with our sex life and convince her we explore more without making her feel bad about it?