???

I would assume it starts when you make your first input, which would ideally be a movement key or pulling out your weapon.

I usually spawn at the bottom of the base? So would going up the base also count in the timer?

Like I said, timer starts on first imput so coming up the tower would count. Don't know why you'd use a run where you spawn bottom of the tower though, all/most WR's spawn on the top 2 layers.

what category bruv

So what they mean by the first input is when you lets say press W (forward). In short, when you start moving, the timer starts. Of course, it depends on what category you mean.

No, the timer starts on the first explosion either by rocket or bomb. In kill categories it starts on first movement, although you are allowed to reset your character until you get the desired spawn location

in the win category im pretty sure it starts on first movement

Well, for the win category it says that the timer starts when the game resets and for the kill category it's on first movement. I'm sorry, but what do you mean by first explosion @Grump ?

private server timing is what grump is talking about

read the rules on the category you want to speedrun i cant help you otherwise as what you said is too vague

The category rules will pretty much explain everything you need to know about timing the run so yeah just read it like toop said