No! First, the “X” in “Planet X” stands for unknown. Pluto was called Planet X before it was discovered. So all planet X candidates are only possible planets. None are confirmed yet and there have been many planet X candidates that were disproved, over the years. But one might exist, the so called (rather misleadingly) “Planet 9”. There are a few other possible ideas too, such as the idea of a planet to explain the “Kuiper cliff”.

However, if it exists, this is its orbit.

Do you see that blue circle in the centre? That's our entire solar system out to Neptune and Pluto. The red ellipse shows the possible orbit of Planet X / Planet 9. And the only way it can exist and not be seen yet is if it is at the furthest point from the sun right now, or close to it. So it is absolutely no possible threat to Earth and the idea that it could be due a flyby of Earth this September is totally absurd. Can you see that? For more on that see Why This New "Planet X" Is No Threat To Earth :).

The other planet X candidates are all similar, have orbits that never take them inside of Neptune. An orbit that crosses both Neptune and Uranus’s orbit would be unstable as there would be no way to avoid multiple flybys and it would only last a short time, because every flyby would change its orbit in a random way.

One that passed Jupiter and Saturn as well like this “Nibiru” idea would be even more unstable - it couldn’t stay in its orbit for more than a million years, so all such planets must have been cleared out in the first few hundred mllion years of our solar system. That’s why all the astronomer “planet X” candidates have such distant orbits.

If there are any planet X candidates out there, they are in stable orbits and they are no more able to hit Earth than Neptune or Jupiter.

Also they must be a long way out to be not detected yet. This “Planet 9” would have to be close to its furthest point from Earth. That’s because we’ve had multiple all sky infrared observations and any nearby planet, close as Pluto say, would be detected easily. At that distance we can currently detect most objects of about 100 kms upwards.

Also Why An Extra Planet Can't Be Hidden Behind The Sun Or Above The South Pole

And: World Did NOT End On 29th July! AWFUL "Silly Season" Story - Journalists Please Be More Responsible