Being rate limited (status code 429) after one API call

[Uraniumless]

Hello, I'm developing a ChatBot that recommends songs according to the users mood (it's a project for a class I'm in). I'm trying to fill a database of tracks and want to include their valence, energy and danceability so the mood of it can be determined. 

However, I keep being rate limited when I call the audio-features endpoint after only one call (https://api.spotify.com/v1/audio-features/) and I have to wait around an hour to be able to call it again (there's no Retry-After header either so I can't know for sure). Other endpoints I'm calling right before this one featured-playlists and playlists (to retrieve random track ids), but they are not being rate limited at all. Do you have any idea of what might be causing this?