Phone screen keeps acting like I’m touching it when I’m not

Make sure the display is free of water or any liquid that could be interfering with the touch sensitivity. Then restart the phone by following the instructions in this article - https://support.apple.com/en-ie/HT201412

If this doesn’t work you’d want to get the phone checked out at an Apple Store or authorised provider, sounds like a faulty digitiser to me at that point.