When the rocket was launched, it was slow at first, or was it taken in slow motion?

This is not slow motion. This is the speed from the beginning, and it will get faster and faster in the future.

The rocket was so slow at first, getting faster and faster. This is an acceleration problem. The rocket is stationary at first, and will rise when the thrust exceeds gravity. When a rocket is powerless or unbalanced (such as gravity and support), it will keep moving at a constant speed or be at rest. When the thrust exceeds gravity, the initial velocity of the rocket will accelerate from 0, such as 2m/s in the first second and 2+2 = 4m/s in the third second.

Another reason why we see slowness is the distance between observers.

For example, when you see a rocket with a length of 120 meters, you are about 800 to 1000 meters away from the rocket. At this time, its moving speed is assumed to be 20 meters per second, but you feel that it is still very slow because you are too far away from it.