It's important to immerse yourself in your field, it's also important to reach outside of your niche for inspiration.
Try this for practice. Browse a news site, such as Google News, through the perspective of your podcast content. Don't look for things that are directly related to your topic, instead look for things that can be springboards to other ideas, even if that idea has absolutely nothing to do with the story you saw.
For example, a podcast about cooking may find some content inspiration from health concerns in the news. This could lead to direct connections between cooking and that health concern. But that health concern could be a springboard to new ideas such as how to keep a kitchen clean and germ-free, how to keep produce from rotting, how to hide nutrition in desserts, and more.
Apply this to everything else you do, see, and hear. You can get ideas from magazines, news, TV shows, sermons, books, conversations, events, stories, and much more.