Inertia is NOT about just standing around doing nothing.
This inertia stuff is weird - it's not at all what I thought.
The way to think about inertia is not to think about standing still. Look carefully at the object and really think about what it is doing. It WILL be doing something - always - but it may not seem that way at first. Then try to work out if what the object is doing has changed in some way. Then you will see what inertia is all about.
Doing nothing isn't always what it seems. Doing nothing isn't always doing nothing.
The clue for me was examining what was happening in the video from space. I could see what happened - and didn't happen when there was no friction or gravity.
I found the best way of thinking about this was to think what was changing - or what might change if it could.

I think I got it when the LabRat
fell through the floor.

Here are some comments from other pupils and teachers that may help you to investigate
First Law