Curious, does he usually bat leadoff? There are a few spots in the lineup that typically require a different approach/mindset and, of course, leadoff is the most prominent.
Aside from that, yes, it certainly happens where a hitter is just frozen in a situation where he usually pulls the trigger.
Hitters work on a thousand different things, mechanically and mentally, and then are asked to narrow that to just one thought when they step in the box in a game. On top of that, the situation changes every pitch. It is, IMO, impossible for a hitter to be able to successfully accomplish that "one thought" process 100% of the time. Once in a while, another thought will creep in and cause lost focus. This can result in the "freeze". Strive for success 100% of the time on proper mental approach - accept 99%. When that one happens, know it's done and move on to the next.