Usually dry air makes statics. Not much you can do about it. If you don't use a dryer, it might help but does not really matter in my opinion.
When I choose fabrics for my tennis apparel lines, sometimes I really like certain fabrics but some fabrics have more static so either I need to choose more thicker fabric of same material or completly change fabrics.
How thin is the shorts? Static problem will be gone around spring.
Men's Tennis Apparel