riddle - Sometimes I am born in silence

Sometimes I am born in silence,
Other times, no.
I am unseen,
But I make my presence known.
In time, I fade without a trace.
I harm no one,

but I am unpopular with all.

What am I?

Answer

You are a

fart

Sometimes I am born in silence,

There can be silent farts.

Other times, no.

There can be noisy farts.

I am unseen,

No one can see a fart.

But I make my presence known.

Farts can smell.

In time, I fade without a trace.

The smell fades away over time.

I harm no one,

Farts are not harmful.

but I am unpopular with all.

No one likes a fart.