iPad Air bought new at release, wifi only, cellular turned off. This ipad is on ios 11, but the lag was happening on ios 10 too. A few months ago I began to experience laggy typing, mostly in Safari. Got so bad that I reset this ipad to factory last night (settings and content, did not restore its prior backup but did sign intoiCloud and iCloud photo library.). The typing lag is still happening without installing any third party apps. Funny, as i was typing this post, the lag improved then disappeared, but it will be back. I can't see why this would be a hardware problem. I have eliminated third party apps. Happens on all wifi systems, not just my usual ones. Could there be some problem with my iCloud account??