a coma (a.k.a. a comet trail)
A phenomenal riddle (the title)
The passing of a comet is an astronomical phenomenon
I'm a natural wonder, hitched to a star
The trail of a comet appears when it enters a stellar system: the stellar radiations 'attack' its outer lair (which is why the trail always faces away from the star)
You could say I’m like an electric car.
Not sure about this one, but at a stretch: they are silent when they move (no sound in space), just like electric cars
I’m hard to see, and some think I’m rare.
In order to spot a comet, you have to be at the right place and the right time on earth hence they are difficult to see. There are many more comets in the solar system than we can see (at least 6000), which leads us (people without NASA's resources) to think that they are rarer than they actually are.
I’m so fast, you may wonder if I’m there.
They fly fast through the sky, blink too long and you'll miss them$\dots$
You can try to find me where the outlook is flat,
It's easier to spot away from all human light pollution (e.g. over the horizon of the sea 'where the outlook is flat')
At the end of the day, your chances are fat.
This is stretching again, but at the end of the day you are more likely to spot the Perseids, which is a meteor shower caused by debris from the Swift-Tuttle comet.