Instagram influencer — hey, she’s got 12 million followers, folks — opened up about aging while promoting her buzzy new comedy-horror TV series “Shining Vale,” co-starring Greg Kinnear and Rob Morrow and premiering March 6 on Starz.“I feel like I’m young. I have a lot of friends in their 30s and I don’t think about it. To me we’re the same age until I actually study it,” the enduring sitcom star, 57, told the Sunday Times Style magazine.And when it comes to turning the big 6-0, Cox exclaimed, “Oh God, it’s so hard to even hear or say.