Before trying a full motion with the grip, get the feel of the continental first.
Try very softly dribbling a ball off the court while holding your racquet in the continental with a very relaxed arm. Do this until you're very comfortable w/ it.
Watch how your hand and forearm rotates like turning a doorknob counter clockwise if you're right handed.
Then you can take your normal service stance at the service line, holding the racquet in the continental grip, get your racquet arm up in the "trophy position" w/ your the left side of your body to net. Then toss the ball and softly hit the back of the ball with a relaxed arm while allowing that doorknob turn motion to occur and square the racquet face to the back of the ball, overhead.
If you can do that back up a step hit a couple more, and continue that pattern until you're at the baseline.
Then do those half motions from the baseline until you're comfortable with making consistent contact w/ the back of the ball.
When you're comfortable with contact from the baseline try your normal motion slowly, emphasizing a relaxed arm. If you mess up go back to the 1/2 motion til you are comfortable again, then back to a slow relaxed full motion.
Don't go full speed until you are very comfortable in the grip making square contact with a relaxed arm.
Good luck.