This is so weird, I used to do something similar when I played piano as a kid. When I would start a passage sometimes and would pause in the middle, I had a hard time mentally hitting the keys again to continue and it felt like the equivalent in my hands of blocking on a hard consonant in the middle of a sentence. Eventually I grew out of it, I play the piano fine now. But it always struck me as a weird kind of synesthesia-type deal.