Lately I've noticed that each time I ask Sonny for a canter, he'll practically go into a gallop (he's actually gone into a gallop 4 times on me so far) and then after maybe 10 steps (sometimes more) he'll go back down into a canter and be fine. It's just when I first ask him to canter for the day...if I ask him again, he'll canter fine.
Strange thing is, is that if my friend or someone else gets on him and asks for a canter, he behaves. He doesn't try to speed up unless they tell him to.
It's really starting to get annoying. I want to be able to canter him, but with his speeding up close to a gallop when I first ask, I don't want to canter with another horse in the arena, due to I'm afraid that he'll get too carried away and not listen to my cues if I tell him to turn and go around a horse. Thankfully he still listens to me cues (minus half halts, or trying to slow him down in anyway).
I do lunge him before hand, and have him canter around. So it doesn't seem he has an over ammount of energy.
It isn't due to an poorly fitted saddle, for when another person rides him, they use the same exact saddle. Everything fits fine.