The typical CE4 is a top coil device, and they are prone to that.... since the wick has to fight gravity to "pull" the juice up to the coil. Thicker juices have a harder time.
Haven't used top coils in a long time, but maybe practice the tilt and swirl? Hold it close to horizontal and "roll" it back and forth a bit so the wicks get covered in juice, then return to vaping position. Might help.
It's possible, too, if you have a variable battery, that you just need to set it a little lower.