Blower motor for central air runs normally for 20-30 minutes, then cycles on and off every few seconds. Fan and compressor in outside unit continue to run normally. Attached jumper wires to R and G and Y thermostat terminals with same result. Blower motor feels hot to touch. Does blower motor need replacement?

The blower motor capacitor could be at fault. It is the cheapest item to try and replace since you probably do not have a capacitor testor.