Our washer doesn’t spin

We have 11 years old roper washing machine  It is not heavily use, there are only two persons in the household. We replaced the lid switches not too long ago and the coupling. Now it doesn't spin by its own. I can hear the motor is trying but the agitator is not but if you manually turn to assist, it turn and it will the cycle. It is an intermittent problem.  Do you have an idea or have you ever encounter with this kind of problem.  Thank you very much for your help.