This is a known and growing issue across all 3 years of iPad Pro models.
I am more than convinced, now than ever, that this growing issue is NOT hardware related, but either iOS 11 and/or iOS 12 related bug.
Maybe both a combination of an iOS issue as well as perhaps an isolated hardware issue.
I have a 1st gen, 12.9 inch screen iPad Pro still running iOS 10.3.3 and I am NOT experiencing these recent intermittent touch screen issues.
Some Posters/Users have stated here that this unresponsive touch issue started sometime late in the iOS 11 update cycle, but seems so much more pervasive in iOS 12, now!
There is, at least, one of these “iPad Pro unresponsive touch screen issues” posts a day!
Currently there is no fix/solution, as yet, from Apple.
This unresponsive touch screen issue affects a small, but still growing minority of iPad Promodels/users.
At least, well over 1000 users, to date, have been affected by this iPad Pro unresponsive touch screen issue.
On the main iPad support community post listings page, in the upper, long search box search for more info about your ongoing iPad Pro touch screen issues using the search terms
iPad Pro intermittent touch screen
OR
iPad Pro unresponsive touch screen
The best you can do is alert Apple to this growing issue.
The only way to get Apple to, DIRECTLY, listen to you is to use their feedback portion of their website.
iPad Feedback
http://www.apple.com/feedback/ipad.html
Cognizant Apple employees read ALL feedback generated from all of the various feedback pages and transfers the data to the proper and responsible Apple teams and personnel , but NO Apple employees will ever respond with any type of direct, individual replies from the feedback you post.
The more users that post product feedback about any product issue, the faster Apple can keep working on a fix/solution for a future software update.
Also, you may want to phone contact Apple, directly in Cupertino, California, and calmly talk to an Apple customer service employee about this issue via the link below.
Contact - How to Contact Us - Apple
For your 2018 iPad Pro model, there is a working temporary user fix to this unresponsive touch screen issue.
Go into the Settings App, General Settings panel.
In the right column, tap Accessibility.
Then, in Accessibilty, look for the Tap to Wake feature and toggle OFF this setting.
Then, immediately restart/reboot your iPad Pro.
Your touch screen issues should go away with the Tap to Wake feature set to OFF.
For any older iPad Pros with the older Home button design, there is absolutely NO type of temporary fix for the unresponsive
touch screen issues on those older model iPad Pros.
NONE!
Best of Luck to You!