Infrared ony stays on for 2/ 3 seconds then switches off for a few seconds then back on …and keeps repeating?
Is there any light (porch light, street light, neighbor’s light’s, etc.) in proximity to the camera? It could be cycling because it’s sensor detects light/dark right at the “sweet” spot between infrared on/off.
Maybe try, just for an experiment, moving the camera or at least point it where there aren’t bright objects in it’s view.