Yogurt Fail Questions
The point of heating the milk to 180F (and then holding it there for a few minutes) is to denature some of the milk proteins so they will participate in the yogurt structure and improve the texture.

You wrote that you added milk powder. This is a good thing because it adds extra protein. It is perfectly reasonable for there to be enough protein that simply heating it will form a loose curd. Acidifying the milk would produce a more firm structure for yogurt or cheese, etc.

Milk can also curdle prematurely if it has accidentally acidified already. For example if it has started to spoil from a mixture of wild bacteria. If your milk is of questionable freshness then I would recommend throwing it out to be safe.

If you are confident that your milk is fresh and has been handled well, and if the curd is fragile and tastes like milk, I would recommend inoculating it and fermenting it for yogurt as normal.