T.D.
He could have sensory issues, my son had this and still does at 5 years old, we actually had to rub him all over kind of making a friction on his skin and then attempt the new sense again. outside is a BIG one, there is the sun, and the wind and the noises and the smell...everything is just different. I would rub him down, and then take him out. 5 minutes no matter how he is acting, and then bring him back inside. Do this several times a day on a nice day, and even if it is raining out as long as it is warm I would make a mad dash outside with him, and then back in. You sometimes just have to warm him up to his senses!!!!
Good Luck!