Yep, Lacey's the exact same way.
She has, what I like to call, her "winter personality" where she's relatively laid back, never spooky, and relatively dependable. Then, she has her "spring personality" where she's just looking for opportunities to spook violently at something, bolt, be resistant, etc.
She's a pain in the summer/fall as well but she's bonkers in the spring.
Right now she's in the throes of "OMG, SPRING!! I feel so young! I have so much energy!!". Overnight we got about 5 inches of snow so she stood in her shelter all night, building up energy, and, because of the snow, everything looked different (obviously terrifyingly so) on our usual route. I had to use my crop on her and the curb rein of her pelham, I haven't had to use either in quite a while. Everything was either a reason to bolt backwards (crop) or bolting forwards (curb rein).
Ah, our horses. Good thing your boy is a gelding and you live on the other side of the country, him and Lacey would have the most terrifyingly split personality babies.
Good for you for sticking with it! That takes some nerve. And just think, our sassy horses are going to make us be pro riders in no time.
I have that same thought process too: maybe Lacey's thick winter coat will help her stay sane-r because she gets too hot? Apparently not. Haha
I love my synthetic Aussie for just that reason, there is no falling out of that saddle. Once you're in it, you're in it until you decide to come out. Hahaha