DIAGNOSIS The wobble is almost never a bent motor shaft. The most common cause is debris lodged in the chuck jaws or a bit that is not seated perfectly straight and centered.
FIX Remove the bit. Open the chuck jaws fully. Visually inspect for any metal shavings, wood chips, or debris inside. Use compressed air to blow it out. Re-insert a known-straight bit (like a new drill bit). Hand-tighten the chuck firmly, then give it an extra quarter-turn with the chuck key if available.
IF THAT DIDN'T WORK The chuck itself may have worn internal parts or was not assembled squarely from the factory. Confirm the wobble by running the drill without a bit. If the chuck body wobbles visibly, the chuck requires replacement. It is a serviceable part.
HEADS UP Avoid using the drill's hammer function with standard drill bits, as this can accelerate chuck wear and contribute to runout. The hammer setting is for masonry bits only.