53 year old woman has symptom of intermittent urination for years. Pee all the way, stop at almost the end, then weaker stream. What's the cause?

Depends. Its hard to answer this question without a good history and physical and some tests. This could be secondary to infection (although unlikely if years), obstruction (cystocele, primary bladder neck dysfunction), behavioral, medications, and neurological. This are a few general answers on the differential.