Instead of 1, 2, 3, 4, in your head say "left, middle, middle, right." Repeat until natural, then change it to be "this one, this one, this one, this one." Repeat until natural, then repeat some more until you can do it by the pattern alone without verbalizing anything internally.

Or don't think of it as counting, just think of it as a drumbeat. Bah-bah-bah-BAH. Bah-bah-bah-BAH. Make sure to go slow enough that it's actually four seconds and not two (whole beats, not half-beats). But the end goal is to not have to think about it at all. It may require thousands of repetitions.