Hi,
In my understanding Dasha Sandhi is a few months of time-period (3-6 months)when effects of upcoming Maha-Dasha lord start having some effect. It is a time to understand, realize and be cautious… as also perform remedies (where needed/relevant) for the upcoming/changing times. This is usually relevant when one is switching to Maha-Dashas of Krura or naturally malefic planets/grahas.
So, I’d suggest that you try to read more and get a better understanding of the concept.
Take care…