The grip on the cue is very important. However most beginners have a poor grip and the most common problem is that the player holds the cue far too tight.
A good cue action relies on the cue going back and forth in a straight line. If the cue is held tight then this becomes impossible. For example the cue will lift up on the backswing and a tight grip can also lead to the cue being pulled into the body.
Most top players have a loose grip. This allows the hand to open on the backswing and keeps the cue online.
The pictures below show the grip during the 3 stages of cueing. When the tip is at the cue ball, the address, the grip will be closed but still fairly loose. At the end of the backswing when the tip is at the bridge hand the grip will open up. Finally on the strike the grip will close again.
Take a look at how you hold the cue. Are you guiding it backwards and forwards in a straight line or are you strangling it? Good luck.