Car wouldn't turn over but all of a sudden it turned over fine?

a week or so ago i filled up my 1990 ford bronco II with gas, put the lid on tight and drove home running perfectly fine. So then I left my car sit for a couple of days in about 85-90 degree weather. I go to start my car, and it wouldn't turn over. It wasn't sputtering or anything, just wouldn't turn over. Feeling sad because I thought my car is broken, i leave it for another day by itself outside. I figured it was worth a try to start it, and it started perfectly fine and has ran perfectly ever since. What happened?