Hmmm, you can still shake it and see if it’s the cables as @PhilDAS suggested.
I had this problem & wrapped some cables with electrical tape where they rattled against the handlebars. Toned down the sounds a little.
@GideonPARANOID started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Hmmm, you can still shake it and see if it’s the cables as @PhilDAS suggested.