I am trying to set up a small scene.
When I press play, all of my props that attached to my character start flying around. Other characters start floating, also.

Is there a recommended tutorial that explains the details of the timeline?

From your description it seems that the Timeline was not at frame 1 when you added/adjusted assets to your scene.

If you start to make any changes to an added asset at any point other that frame 1 then that asset will have keyframes added to the Timeline. This means that said asset will start animating from the frame 1 position up to the keyframe position added when adjusted.

You can correct this by making sure that the Timeline scrubber is at frame 1 in your present scene, from the menu bar select "Animation > Remove Scene Animation and choose one of the options shown below.

76% of original size (was 662x19) - Click to enlarge




Gerry

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System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.

Thank you. That makes a big difference