If it makes you feel any better, I had that same feeling back about a week ago. And it wasn't nearly as hot and humid as it had been weeks before, but still... I've played so infrequently the past few years that it's basically like starting over for me too.
Pace yourself. Don't panic. Just be smart. Pick and choose when you can get out to enjoy the game, without putting a lot of undue stress and exertion on yourself (especially if it's hot and humid out!). If you take things in moderation - golf (the activity and exercise and the distraction itself) will do both your mind and body good.
Nothing to fear, but just be patient. You'll be back before you know it. 🙂