Since this frictional force will be lower than the static value, the load accelerates until the decompressing spring can no longer generate enough force to overcome dynamic friction, and the load stops moving. The pushing force due to the spring builds up again, and the cycle repeats.
Because the kinetic force is less than the static value, the load speeds up until the decompressing spring cannot provide sufficient force to counteract dynamic friction anymore, causing the load to halt. Then, the spring's push accumulates again, leading to a recurring cycle.