If the sun were to suddenly vanish in our solar system, it would take about 8 minutes for the Earth to exit its orbit. This is because the gravitational field of the sun would vanish at a rate of $c$. I am basing this on a question where the sun suddenly disappeared.
However, suppose the sun was already present for, say, a million years. If I were to suddenly add a massive body, such as a planet, at a distance of 149.60 million kilometres (the current average radius of the Earth's orbit), then shouldn't the planet immediately be attracted to the sun? Would there be a delay? And, if so, why?
This question would also apply to charges and electromagnetic fields since they also travel at the speed of light.