Things happen. Few people stay at the same job forever. There tons of reason why people make changes.
So if you aren’t quitting, what is it?
You are changing directions! You are moving on! There’s no shame. The great thing you are doing is that you are moving on!
If there is shame it’s staying in a situation where you have lost your enthusiasm. It would be staying in a situation you hated because you were afraid to look for something better. It would be because you had given up on your dream of doing special things in your career.
It would be because you had totally lost your motivation to improve, make bigger income, or even to eventually have a business of your own.