my vocabulary that is too limited
Speaking will allow you to pronounce only the vocabulary you know :)
Read books. Aloud. Learn a few Polish songs. Play with sounds and feel free to exaggerate them initially to expose yourself to what is foreign to your organs of speech. Eventually, and in regular speech the exaggeration won;t be there anyway.
I am just too shy
That's what happens and that's why I suggested starting out with speaking words when nobody is around. First you need to get comfortable with yourslef speaking Polsh sounds before taking the next step and speaking with Poles.
Perhaps a news station or radio station or some such thing?
That's sounds like a good idea. Sorry, can't recommend other audio material as I neer needed it myself to learn Polish.