The reason you pause is because you're reacting and reaction is slower than action. You react because you're thinking about what to do instead of doing it.
The most valuable tool in your arsenal is your ability to control the situation. When you practice, don't think about the technique; there is no technique. Instead, watch your uke; he'll tell you where he's going to grab. Watch how his nose points toward the side of your body he thinks to grab, or the direction his eyes flicker as he examines you for the attack. Everyone has a tell, even if it's just that moment when he starts to move (that you notice). You have all the time in the world.
When you start to see it, instead of passively waiting to be grabbed, move your hand a little forward to meet his grab; by doing so, you're able to take his momentum and move him before he realizes it. You're now taking control of the conflict, putting him into the defensive role.
As soon as you have contact, move. Move in the happo, the eight directions (4 cardinal, + 4 diagonal – any direction), and this will eliminate choices (after all, you've already started to move). As you step, move your arms with your body. Just move whatever manner feels natural; you're simply eliminating choices. From there, you should simply have something already forming, and you can complete the escape or counter.
The thing to realize is that it doesn't matter. Once that you force yourself to move, you're already breaking that freeze, and you're buying yourself a second. That second isn't the time to make a decision about what technique to use, but rather what your next move is going to be. Just move, and the techniques form themselves.