The Invisible Strangler...The Blue Man???
The synopsis of this movie sounds a lot like another laughably corny movie that I own called 'The Invisible Strangler' (1976) AKA 'The Astral Factor' and 'The Astral Fiend' with Stephanie Powers in the role that Karen Black would play in the later movie. It's about a psychopathic inmate who after reading books on Eastern Mysticism from the prison library learns how to dematerialize at will, thus he escapes and goes on a murderous spree, strangling beautiful young women.
I'M A TRAVELING SALESPERSON. I SELL BANJOS.