This is an infamous problem with modern renderers know as temporal coherence. The slight camera movements cause the light rays to fall in slightly different spots each frame, which makes the denoiser understand each image differently.
Your scene here is one that’s especially difficult for Cycles. It’s an interior scene, with multiple light sources, it’s dominated by indirect light, there are narrow beams of sunlight and there is lots of glass everywhere. Those are all elements that make a render more challenging and noisy (though not impossible, with a bit of knowledge).
Let’s start with the more obvious things you can do.
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Manually pick a “min samples” value. If you leave it at 0, Cycles will choose a value for you based on the max samples, which might not be good for your scene. In an interior scene or a scene with lots of reflections, it’s often good to pick a higher value, like 64 or 128. It will guarantee that Cycles finds the more complex reflections and noise patterns and can sample them properly. Your other sampling settings should be fine for this scene.
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Make sure all your glass shaders use the shadow disabling trick, or this could result in lots of noise.
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I see there are multiple spot lights in the ceiling. make sure those are not made using point lights or emissive meshes hidden into deep holes, or lots of rays will be wasted as Cycles will struggle to find the hidden lights. Use spots or area lights instead, and adjust them to the shape of the hole as well as you can. If you need the light source to be visible, there is a way to make a light object visible to the camera in the object’s visibility settings.
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If there is sunlight entering the room, I suppose there must be some sky light too. If yes, make sure your exterior windows have light portals placed in them, as that will help with the sky’s noise.
Now, let’s talk about a more advanced technique: the double resolution trick.
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1- Render and denoise you scene at double resolution. You can lower the sampling settings so it takes the same amount of time as before, as the higher resolution increases the amount of rays.
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2- Bring the double size images into an animation editing software and reduce them back to the intended size. I don’t recommend the Blender sequencer for this, as it’s image reduction isn’t the best.
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3- The end result is a lot more crisp, with fine details and textures better preserved. It won’t completely eliminate the flickering, but it will make it finer in size.
If you have a good CPU, this might actually be a case of a scene that renders faster with path guiding, it’s built for this exact kind of indirect light dominated scene.