A lot of mishits start in the hands. Too tight a grip tenses the forearms, slows the club through impact, and makes the face harder to square. Too loose and the club twists in your hands.
Light at address: On a scale of 1 to 10, aim for about a 4 or 5. You should feel the grip in your fingers, not a death grip in your palms.
Lead hand leads: The top hand (left hand for a right-handed player) sets the face. The bottom hand supports it. If the bottom hand clamps down, the face often closes or the arms lock up.
Check at the top: If your knuckles whiten or your forearms feel tight at the top of the backswing, ease off. A lighter hold lets the club release instead of forcing it.
If you play only a few times a year, just notice when your hands tense up under pressure and soften them before the next swing. If you play often, a few slow swings focusing only on grip pressure will do more for consistency than another new driver.