If your battery health maximum capacity is close to 83-80%, your battery is reaching (has reached) the critical point of its life and could have unpredictable behavior. Check its status in:
Settings>Battery>Battery Health>Maximum Capacity.
Shouldn't be this case, it could be a hardware (digitizer? other internal component?) failure but we, just users like you, cannot diagnose that issue remotely, sorry.
I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> https://locate.apple.com/choose-country-region . After checking it out, they'll give you all the available options.
Regards
Giulio
(*) You can do it: