mine does also, ive learned to shut it off for 10 min and back on. or until its cool...
happens sometimes to me tho, not all the time.
when it happens, when i leave the house and im driving about,
at first i thought it was wifi searching, so ive set wifi to not search for wifi.
sometimes if the screen is getting hit by the sun.
sometimes a weak 4g signal.
sometimes browsing on 4g signal.
in all my cases, i shut it off wait for it to cool and power back on.
if i dont shut it off and wait for it to cool, my battery dies quickly..
10min wait to cool is not a deal breaker for me.