And my favorite...

"Can I ask you a question:?"

Two sardonic responses from me...

"I don't know...CAN you?"

or

"No." [followed by me impatiently telling them to "Just ask the damn question!" once they appear speechless about my facetious "no"]

Usually, if someone has to preface a question by asking you whether you're willing to answer it...that's a red-flag that the question is inappropriate and/or ill-conceived.

Also, how am I supposed to preemptively tell them whether or not it's okay for me to answer their question when I haven't heard the question itself, yet?

It's like they're asking me for permission to make an ableist insinuation.