Learn English – concise word or phrase for the feeling of being unsure if someone is kidding

I'm searching for a word for the feeling of uncertainty as to the sincerity of another person's statements or behavior.

Or, the state of being that is to think someone is possibly putting on an act without knowing for certain.

"skeptical" is close, but I would like something focused on the sincerity or intent of the message rather than its accuracy or validity.

This may be theater-related, or perhaps more precisely defined in another language. I do not know if it is appropriate to ask for non-english definitions here, though I would be interested in them.

An example of a situation that might produce the feeling I am attempting to name:

Someone publicly declares that he or she has had a book published on snark and sarcasm. This person, contextually, is quite sarcastic but also a known published writer. To consider the statement true or false would be equally rational.

Another example:

A professional comedian known to be critical of news and media does an interview with a major traditional news and media outlet, and he or she is unusually cooperative, respectful, and accepting of the interviewers. He or she is friendly to the point that it is out of character. It could stand to reason they are being sincere to make a point, or insincere to make a joke.