I said "fans" on the beginning because I thought there's 2 but actually there's only one (weird)You said in your first post "fans" but now you say there is only one fan? That's unusual, there are usually two, one large and one small. Both should come on and go off together.
Fan/s coming on fast for a few seconds then going off is often a symptom of low-speed fan resistor failure. or at least it was in the older installations where the resistors were in the fan support struts.
Should...Turning the aircon on should get those fans going.
Fish