Respected Sir/ Madam,
My name is _______ (name) and I am working as _______ (designation) in your reputed company for the last ______ (mention duration).
I write this email in order to request you for demotion from my present position. I have been working as a _________ (designation) and now, I feel that I am not capable of taking the responsibility anymore. The reason behind the same is __________ (mention reason/health issue/age/time limitation/ect).
It is to request you to kindly consider my request and consider doing the needful. I shall be highly obliged.
____________ (Contact details)