I have a 15 year old Morgan I use for trail riding. I am 40 and have been in training for 10 months. When I got the horse I was told he bucks when asked to canter. I just started cantering with him and I have found that he is not bucking with me on him at a canter, but the last two days towards the end of my ride I will ask him to trot and I think he knows that I am about to ask for a canter. But anyways, when I am asking for a more forward trot he is arching his back and striking out his front feet. The first time I rode through it I couldn’t feel what he was doing. Yesterday he did it again but it was even bigger. I felt his back curving and I saw his feet he felt very frustrated? Or like he was protesting what I was asking. I got off him because I didn’t want to be on his back when he was behaving this way and I lunged him. A bit of a backstory when I started out riding yesterday and all days he is very slow- like you would walk faster then he goes he is lazy lol. Anyways, when I brought him to the trailer to get the lunge line he was walking really fast like right up besides me, almost ahead of me, and had a lot of energy for some reason. (I had been walking and slow trotting (he wouldn’t step more forward for the 40 minutes prior) anyways I lunged him he sweat a ton but he choose the speed on the lunge line and I only stopped when he was ready to walk when I asked him to walk. Anyways pain has been ruled out. I am not sure why he started striking out? And or how to get him to stop?