Check the fuse box, should be labeled accessories. Sometimes just a fuse blows or gets carbonized. If problem persists have an obd test and see if there are any stored codes. Loose connections can cause intermittent issues as well, harnesses or plugs working loose. Check those if possible. Many instrument clusters after a while can degraded and need refurbishment or replacement but for now check the EZ stuff! Good Luck!
Search Buick Century Questions
Buick Century Experts