Check the set up angles of your spine, hips, knees and head in order to get into a power position for a power coil and a power swing
A tension filled grip, especially from having the shaft too much in your palms, will kill your entire swing. It stops your wrists from hinging naturally and then works its way up your arms and into your shoulders and locks up your entire swing.
A waggle is a great preparatory motion to get your wrists, elbows and fingers loose and ready to swing