Camera LookAt Interp speed not working when switching on or changing the actor to track

I placed a camera on a rail, my aim was to move the rail, and sometimes look at objects during the journey. Unfortunately, the interp speed is not working when I enable the lookAt settings in a sequence (rotates immediately next frame). Also it is an issue when I change the target actor. Rotating the camera manually not a solution, there will be a little “jump” in movement if I dont set the rotation perfect(usually I cant or very hard).
Is there any easy solution to make a smooth camera movement/transition situations like this?

P.S: It would be nice an acceleration for the interp speed as well.