Question

the velocity of an object at rest is considered to be uniform

Answer 1

it is considered as uniformly accelerated motion

Answer 2

Rest and motion are relative terms.
An object at rest with respect to one observer can be in motion with respect to other.

For example :
 Consider a ball placed on table. It is at rest with respect to table or with respect to surroundings in a room.
hence the velocity of ball is consider to be zero  and it is uniform because it does not change  over period of time.

But for an observer on moon, the ball and table will move as earth moves with uniform speed.
But velocity of ball changes at every point of time when moving in a circular path.So, velocity is non uniform .

Hence with respect to observer only we can say whether the object is at rest or in motion.