B737 first officer reported uncommanded elevator movement in flight.

Attributes
ACN	1632023
Time
Date	201903
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Elevator
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

Narrative:

On climb out through approximately 15;000 feet;the aircraft started to bounce/oscillate up and down. This was not normal and was unsettling. The elevator had been inspected due to a prior occurrence of the same thing. The oscillations could not be felt in the control column. We [advised ATC] and returned to ZZZ uneventfully.

Original NASA ASRS Text

Title: B737 First Officer reported uncommanded elevator movement in flight.

Narrative: On climb out through approximately 15;000 feet;the aircraft started to bounce/oscillate up and down. This was not normal and was unsettling. The elevator had been inspected due to a prior occurrence of the same thing. The oscillations could not be felt in the control column. We [advised ATC] and returned to ZZZ uneventfully.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.