The problem: Horse will not start into spin.
Why does this problem happen? If a horse will not even start into a spin, he has either not been schooled to spin or he has learned to hate it.
How to correct this problem: I go right back to the beginning to ‘fix’ a horse that freezes when I ask him to spin. One of the best ways is to let him “find” the spin like this: I walk him forward and lift the inside rein lightly (not strong contact at all, just enough to let him know something is happening). He may fuss a little, especially if he has some bad memories, but eventually he will drop his nose and turn into the rein. At this point it is absolutely imperative to lower my hand to reward him for complying. I use very little outside rein for this exercise (if he is really resistant, I use none…) and only enough inside until he figures out for himself how to release that little bit of pressure. If I pull hard, he will almost surely pull back so the trick is to just lift the inside rein to take the slack out.
When he relaxes into half turns, I ask for more until he regains confidence. At that point, I can begin to add other corrections - like straightening or speed or pivot foot. I need that first step or two to be willing to be able to advance training.
Note: I can feel very easily the spot where my horse relaxes into the turn - he softens, lowers his head and 'melts' into it. I build on that!