Air carrier First Officer reported that during initial descent the radio altimeter displayed erroneous indications. Reporter stated they did not complete a maintenance write up because they believed the event was due to 5G interference.

Narrative

During the initial descent into BUF approximately 100 miles west of the field at FL290 the radio altimeter briefly gave an erroneous indication of 300-400 ft. lasting 2-3 seconds. After a conversation with the Captain we both thought this was due to the 5G interference given that the RA had not shown any other signs of malfunction and the incident did not re-occur. We made a report to ATC so that they could file it and other pilots in the area could be made aware. Because we did not believe this was an aircraft Maintenance issue we did not consider a Maintenance write up in BUF. The flight continued and landed without further irregularity. If the 5G interference had not been such a recent point of issue and discussion within the industry we would have more than likely concluded that there was an issue with the RA and written it up at BUF; but with 5G in the forefront of our minds we assumed that it was to blame. In hindsight as pilots we are not qualified to determine what is and what is not 5G interference and should have written it up; if even only as a precaution. We had no intention of hiding a Maintenance discrepancy and of course in the moment if we had thought the airplane needed Maintenance we would have taken proper action. Going forward I will ensure that all erroneous RA indication are brought to the attention of Maintenance regardless of the situation.