Why does my iPad get hot when I’m using it?

If available & cost efficient too; perhaps consider an authorized Apple trained service,

~ after testing device, for any other contributing factors: for a battery replacement?

An older device with overheating issues, implies some hardware failure in the works.

The 'energy waste' has to come from a source, a power adapter &/or charge circuit(?)

[My older iPad Mini (v. 1.1 wi-fi) way too old for a fix; runs OK still from local wi-fi base.]

Official Apple Support:  › ipad › repair › service

• iPad Repair - Official Apple Support

//support.apple.com/ipad/repair/service

Probably after reading fine print (actual version iPad is still unknown)..

You may ask a Genius in retail store about the cost. If they'll do repairs

or in marginal cases: may find yourself with a refurbished iPad, at best?

The iPad 2 is an ancient device. I suspect that it is beginning to deteriorate.