I would like to ask for advice in building this world. Basically, it's earth; however one morning everyone but the Main Character disappears. No bodies, no trace. I'm debating between they all disappeared sometime in the night or just as MC wakes up.
During the night- no cars moving or stores opened (stores open super late would be open)
Wakes up- cars that where moving lose control and cause massive wrecks, ovens and burners on cause fires (more chaotic)
I'm currently partial to the one where everyone disappears during the night.
I am also conflicted as to how Main Character (high school senior) figures it out.
It depends on whether you think adding chaos would help add drama or just make things more complicated for your protagonist. Also, everyone disappearing as the MC wakes up implies it's linked to them, while having everyone vanish in the night adds some ambiguity to the situation.
As for figuring it out, wouldn't not seeing anyone around at all clue your MC in?
I want the sense of unease to be maximized, I feel the overnight disappearance would provide that more. Car crashes and burning buildings add a sense of disaster.
MC walks to school, it's a short walk and if he leaves a little early (he would probably do that upon not being able to find parent- first clue) the walk would be very quiet anyways. They wouldn't really start to get suspicious until they get to school. They would most likely assume they forgot a holiday at that point.
Perhaps they decide to head into town and/or visit a friend after seeing school empty, causing them to notice that everything is a mess and nobody is around?
I think it would be fairly obvious from the get-go that something was wrong. A quiet world is naturally distressing to us. Our brains adjust to block out the white noise, and if there's less or no background noise, we kinda freak out. He should almost be woken up by the disappearance. Or a now driverless car could swerve into his front yard, waking him up that way. It should be really easy to tell something is wrong.
Also, is it just the humans that disappear? Our did animals, too. If other creatures are still here, you're going to have to add some things as time goes on. There's gonna be a lot of feral cats and rotting dogs. It'll start to smell REALLY bad.
Also, cattle. If they live in a rural area, farm animals will likely die. Especially cows and sheep, which are true creatures of habit.
You're right, now that I'm focusing on it I can easily hear road noise.
MC could be on edge but not realize what was wrong.
Maybe after they come back from school, assuming its a holiday, they go check up on social media -empty- the news and all the channels are shut down, which is when they start trying to figure out whats wrong