Neck pain after trampoline is due to whiplash.
When jumping on a trampoline, one’s entire body, i.e., legs, torso, neck, head, are supposed to be rigid and the arms are used to maintain balance in the air and at landing.
If the head is held off balance at impact, there will be whiplash.
Go have the doctor check the neck out. Make sure there is no misalignment of the neck bones, i.e., the spinal discs of the neck.