How would you even tell?

I've had the subjective experience of feeling unable to complete thoughts I would like to think through, mostly as a consequence of post-traumatic stress.

It most often manifests as something like "A, therefore B, therefore C, therefore oh look a bird!" repeating over and over, along with an intuitive feeling that all the aborted chains are pointing roughly in the same direction. It sometimes manifests as "A, therefore NOT B" in cases where if I abstract over the particulars sufficiently it's obvious that A -> B, and I can't figure out why on earth I concluded NOT B in any particular instance. (Often followed by "A, therefore NOT B" in the particular instance again.)

I typically describe both of those experiences as my mind skittering off the surface of a thought rather than engaging with it, though the actual experience isn't kinesthetic like that at all.

That said, I don't experience any of that as being at all related to the sensation of "free will" the OP is talking about.