Start-Device, Combination (Sta WP2304885

Hello. The compressor on my Whirlpool refrigerator was not starting and the fridge and freezer were warning up. If i hit the back of the refrigerator with my hand hard the compressor would start and the refrigerator would run fine for a few days. After reading your website i replaced the starter relay and the capacitor. The unit ran fine for about a week. Now we are back to compressor will not sometimes but does then i hit it. Any ideas on the next part to replace? Thanks mark