My most productive is honestly when I'm on a caffeine high (my personal favorite is a 24oz NOS). I have pulled all-nighters. Accidentally.

But getting INTO the mood for programming is simple and kinda embarrassing. I get excited by seeing programming keywords in real life. For example, at a job I worked at, there was a whiteboard what had the word "include" on it forever. Not about programming at all. But every time I saw it I was reminded of c/c++ and it made me wanna do some code. I don't know why I'm like this.