I can tack up and mount easily, but as soon as I get my other leg off the ground to swing up, he starts walking. He has never done this before. Maybe it's a loss of respect, but I'm not sure. Now something different; I noticed this the beginning of the week when I went riding in the snow. He was walking and swishing his tail like he was going to get down and roll with me on his back! I immediately pushed him forward and he got a little angry and would start hopping around if I tried to push him any faster than a walk. Again, the next time I rode there was no snow because we got a lot of rain and it was like +12 degrees celcius for a few days. I lunged him before riding this time for a good 15 minutes of cantering and trotting to get any kinks out. I hopped on, and he once again started with the tail swishing and putting the head down. I hopped back off and lunged him again and checked his movement for any sign of pain but I couldn't see any. I got back on and he acted a little more normal.
I had a professional/vet at the barn I board at check him for any pain and to see if my saddle still fit properly and she said that everything was fine.. The 3rd time I rode he did the exact same thing. Any tips?