A couple of days ago, after powering up my Pixel 4a it felt scary hot. As if the battery was being drained… which it was, but by what?
I wasn’t using the phone, and no apps were running, and yet by 6 PM the battery was down to 8%. I charged it back up and turned it off. Since yesterday morning it’s been behaving normally.
Other users have experienced the same behavior, but there is no official explanation from Google that I can find. If it’s a battery maintenance routine, why would it run without notice? As long as the battery doesn’t fail and bulge out — as happened with one of my old tablets — I won’t worry about it.