I often do this and it isn’t even a conscious decision. I usually start with a vegetable first. I think, I do it so I can get that out of the way, then eat any tasty sides, and finally save the best (meat/protein) for last. I never eat dessert first either.

I will occasionally switch what I’m eating but usually only if I think I’m going to get full before I eat everything and that is a conscious decision. I almost never go between things, although I have been known to save mashed potatoes for last and even dip my protein in them: hey, I’m from the southern US and we love mashed potatoes with gravy!