I also make instrumental music, and I have this same problem. What I do is: find a word or phrase that matches the rhythmic phrasing of my main melody. That becomes the working title.
An example is how Paul McCartney’s original title for “Yesterday” was “Scrambled Eggs,” since those words fit naturally over the start of the melody.
An example is how Paul McCartney’s original title for “Yesterday” was “Scrambled Eggs,” since those words fit naturally over the start of the melody.