What age to puppies enjoy walking?

HI all,

My 4 months 6 day* old miniature pinscher puppy still is scared of the outside world and we have trouble going for walks. I had a nice 15 min walk with him yesterday, but today because of the wind he won't budge. Things like wind, excessive noise, too many people, will determine if he wants to walk. I know socialization is important so when he doesn't want to walk for any of the reasons above we just sit together outside for a long period of time while he watches and barks. I also try to get him in the car if I'm going on a quick errand - he does so well in the car.

I'm worried he isn't getting enough exercise. I have been diy-ing enrichment toys with egg cartons and tissue paper as well as freezing his kibble in his bowl so it keeps him occupied ( I also have various Kong type toys). I know these enrichments help stimulate a dogs mind but it doesn't feel enough in terms of moving his body. We do play with him a couple times a day where he gets a couple zoomie periods but again, I feel like its not enough. He is turning into a couch potato like my 13 yr old min pin. Is this normal behavior for a puppy this old and when do they actually want to be outside other than just potty.

EDIT: sorry everyone, 4 months and 6 days not 4 months and 6 weeks haha