I feel my implant slightly wobble when I chew. Is this normal?

It could be a loose screw, weakened crown bonding, or the implant fixture itself shaking due to alveolar bone resorption.
A loose screw or weakened bonding can be fixed simply, but if the fixture itself is loose, the implant may need to be redone.
Even simple problems become harder to solve if left untreated, so it is best to visit the dentist immediately.