Uniform motion is the motion in which an object travels equal distances over equal time intervals. An easy way to determine if the motion of an object resembles the uniform motion or not is by a simple experiment in which the distance traveled by an object is measured over equal time intervals. If the experiment was carried out using a toy car and a recording timer (with a ticker tape), one can calculate the distance traveled over given time intervals. A plot of distance vs time will give us an idea of the uniformity of motion. A straight line (irrespective of its slope) will indicate uniform motion.
In general, if study the motion of toy car from start to stop over smaller time intervals, we will see that the motion is not uniform. This is due to minor acceleration or deceleration or change in direction (even if it is minor), which may cause non-uniformity. The car starts and picks up pace, its motion is somewhat steady and then it decelerates to stop; all of these phases may not be very uniform.
An easier example of uniform motion is your car traveling in cruise mode.
Hope this helps.