Some horses spook to see what the rider's response will be and also to see if it can be a way to get out of working. Some horses learn how to get the best of riders that give up easily compared to riders that take the reigns and keep them on track with doing what the rider is asking.

He is just showing you what he has learned and you are a smart enough rider that you will train him to do whatever routine "you" want him to do which will include your getting in shape while he learns to do what you want as you work on getting in shape to slowly develop a schedule for the both of you. Perhaps on the days that you don't quite feel up to riding you could lounge him and ground work him so he gets to know you that way too.

It's so nice to hear he comes to you and likes to be near you.