I can write memoir pieces fluently, and I'm pretty comfortable writing fiction in first person as a result of that, but for some reason when I transition to third person I just get stuck and become frustrated. When I read third person it seems pretty straightforward, but I just feel so shackled when I try to write that way. It's frustrating because the novel I want to write and have put so much planning into really needs the openness of third person. I've experimented with different forms of third person (I leaned towards Limited, as the thoughts of certain characters are pivotal) but I find it very hard to establish a voice. My biggest problem arises when there is a section with no speech. I relish and enjoy dialogue but in a story with a lot of actual things happening, not just people talking, I start to struggle with how it's written and spoken. My writing feels a lot clunkier and I struggle to impart any of my strongest literary qualities onto the page. I've been reading Mistborn by Brandon Sanderson as it's the kind of style I would like to use, but when I sit down to write it just doesn't happen the way first-person does. Has anyone had these kind of problems and found a way to overcome them?
Personally, I've never had too much trouble writing in the third person, but I did have quite a bit of trouble when it came to long paragraphs of actions, as I felt that I always either went too beige or to purple on the prose, never quite fulfilling the description of the scene the way I intended it. The short-term solution I found for it for my series I was writing at the time (based on spaghetti westerns, a long time ago) was to interject the narration of the punches, fights, shootouts and similar stuff with long descriptions of the tension surrounding the characters, in pretty much a Sergio Leone-esque literary homage. I still do that when I start a fight in a scene, but I spent the time training my writing to better describe actions and longer dialogue-less scenes, and I found that the use of commas and the word "then" really made my writing seem quite stilted when it came to actions, as writing with a more "and he punched Groucho in the face and Harpo slapped him in the ears, which made him angry. Groucho jumped on top the table and kicked Harpo and laughed with glee as his nose started bleeding" kind of instant-action sort of feel made me feel much better about the scenes. So, I guess the answer is just practice. Try to make longer sentences that run on for more than your customary, to make the reader "out of breath," so to say, and see what works best for you.
I think it's a matter of just training yourself to write in third person, if you're used to write in first. I wrote in first person when I was younger and struggled like you do now when I realized I needed third person since I wanted to tell the story from three people's POV. It probably won't come out the way you want at first but practise makes perfect. As for the scenario you describe I think third person actually would be more fit to describe things that happen when people are not talking. (not sure what kind of things you're talking about here)
Have you tried writing a piece in first person and then converting it to third person with minimal changes? I'm not suggesting that you write a whole novel that way; just as an exercise.
I like @ChickenFreak 's idea. You mention the "openness" of third person, but there really isn't anything you can do in third that you can't do in first, and vice versa.