Developing projects: is it better to build a MVP and refactor from there, or to design extensively and build from that design?

Question

MVP meaning minimum viable product, such as a project that was developed relatively quick but requires extensive refactoring to be clean. I noticed on a number of projects I have this dillemna: is it better to spend a small amount of time (~15 mins) and code a working version, and refactor from there, or to design the whole program and develop it based off of that design? I am having success with the former, and I think the latter is a good idea too, but I find myself designing too long or changing my mind about it's structure so often many hours may pass without me typing a single line. Which one is preferred, if any, and how? Is it normal to spend long durations on program design?