My dog is suddenly scared to go for a walk?

This started about two weeks ago, I didn't think much of it because we had been getting a lot of rain lately, which scares her. But now that the weather is nice I take her to different parks, all of which she has friends at; but once she gets out of the car and walks for 5 to 10 feet, she then wants to head back with her tail between her legs. She is a small 4 year old Shih tzu by the way, is very playful and loves seeing her friends at the park. There has been nothing traumatic that I can think of that might have made her scared. She used to love walks, sometimes going on 3 a day but now she's terrified.