Phone gets warm

[Sproz]

So I've noticed for the past 2 days, my phone gets rather warm in the middle of the night when i leave it plugged in to the charger. 

I charged my phone close to 11pm last night and i unplugged it past 3am. 

I have battery protection turned on where it would only charge again when it drops below 95%. 

The phone gets warmer than when compared to i use the phone while i am charging. Is this a normal behavior?