its likely the sunroof drains, the hoses sometimes shrink and the grommets
on the end of the sunroof drains clog and back up, water will build up in
odd places when this occurs
pull the panel off the windshield pillar and check the hoses for shrinking
then try and blow them out, if the tubes are hard or shrunk replace them
if the grommets are clogged blow them out and run soapy water through them removing/installing them is very very difficult
then stop parking under trees and keep the sunroof gutter clean