Yes the quinoa is a starch.
If you need to watch your starch intake then you should not eat too much quinoa but some quinoa in moderation is still okay even when you are not supposed to eat much starchy foods.
The quinoa contains carbs also which mostly consist of starch.
Besides the starch in the Quinoa the Quinoa also consists of things such as insoluble fibers, and small amounts of sugar and resistant starch.
So yes Quinoa is a starchy food.
Quinoa is very healthy for you though so if you don't need to watch your starch intake then you can eat a lot of Quinoa and reap the health benefits of the Quinoa.