If the actor read the script, prepared for the scene, has done rehearsal,… there is rarely a suprise with a scene.

It can happen, that the scene simply doesn’t work and a new way needs to be found to make it work. This happens by improv or re-writes. Feeling uncomfortable can also be used by an actor to improve the scene. However, that doesn’t work with an inexperienced actor.

Bottom line: actors know what they are signing up to, there shouldn’t be any suprises. Of course there are exceptions.

Photo from Alien 3