I have a rheem rrpl-b036jk10e package unit. The blower Moter will only come on for a couple seconds and will not come on again until the power is shut off then it only runs a couple seconds. I have replaced board, contractor and thermostat. Anyone have any suggestions

Check to make sure the motor is getting correct voltage when it shuts down. Check motor run capacitor. You have wasted enough money changing components that were not in need of replacement. Maybe time to call in an onsite hvac tech?