Are moral values circular ??

If I say I value sentience as one of my fundamental values of life does that make my argument circular when someone asks me
why do you value sentience?
Well because I just do ?
Does that make my argument circular and invalid ?

Circular arguments are not always fallacious, and this bothers many people. This gets heavy into philosophy when the concept of self-evident truths need to be considered. We value sentience because it is self-evident. There is no circle, it is an endpoint (or beginning). You can make the same claim fallacious if you were to say you valued sentience because of of something like "your mind," because the mind is, essentially, sentience. Another problem arises when people attempt to claim "self-evidence" where none exists, like "Obviously, it is self-evident that Joseph Smith was the all-American prophet!"

One other point beyond the scope of this site, values are affectively influenced , meaning they are basically based on emotion. The process of justification is a rational process, and values are largely non-rational. This means that values cannot always be justified. That isn't a problem for the person holding the values; it is the problem for the person demanding such values be justified. If someone values "freedom" over "safety," we can talk them through all the arguments for better gun control, and their values might change as a result based on information they did not have before. This is the best we can do when it comes to "justifying" values.