Actually, I have kept Kenyi's for 5 years, and successfully breed them twice. The shaking is a mating thing. it is to draw the female to take the males anal fin (egg spots) in its mouth. This allows the male to fertilize the eggs already in her mouth. Juvinilles will practice this often, I have even seen females to do it. If they observe this from an adult they will do it more often.
What Alyxx said about rubbing, in some case you do need to worry, HOWEVER, Kenyi's normally rub against decor as a way of establishing territory. They also dig through substrate, and often itch. I would not freak out everytime I saw a Kenyi rub against something, especially if there is another fish nearbye, or if he is rubbing the same place over and over, It can also mean parasites, but I would not conclude parasites in Kenyi cichlids off of rubbing alone, they rub all the time, especially if they are trying to claim a territory.