So this is weird but it seems like it went away. As weird and strange as this might sound, in my case and probably you’re too, it’s your actual Instagram account.
I deleted and logged out completely of my original Instagram account and made a completely new Instagram account. I logged in with the brand new instagram account tested it out and my phone doesn’t heat up while using instagram anymore. The moment I log into the old account my phone starts to heat up again. It worth trying trying it. Let me know please