Do you have a chance to get to know PhD students who are teaching? I went to a SLAC, so my professors always seemed fairly approachable, but after I started making friends who were TAs and PhDs themselves, I realized that any last remnants of intimidation started to go away because, in essence, I had beers and went to the movies, etc, with their future colleagues all the time.
Yes, your professors are more experienced and knowledgeable, and might be far further along in their career than anyone near your peer level. But they also like the same popular TV shows and sports teams, might be on facebook, make mistakes... maybe keeping these things in mind might help when talking to them. Or maybe your problem is far deeper, in which case, the earlier posters have good advice.