This is nimblewill, a grassy perennial weed. As you've noticed, it dies down to the roots in winter and greens up again in spring. It is difficult to control. Since you don't have too much in your lawn, it may be worth trying to control.
You can kill the patches with an herbicide containing glyphosate and reseed, or you can use Tenacity (expensive). You can also hand dig, which isn't as crazy as it sounds when there isn't too much yet.
Try to prevent it from going to seed.
Click here for the full fact sheet: http://extension.umd.edu/hgic/nimblewill
What a great resource, Thanks so much.