Sweating in his sleep

[Blueuggboots]

My DS is 3.5. Sleeps really well. Goes to bed without issue and usually sleeps from 7.45-6.45.
I go in a check on him before I go to bed and he's often wringing wet with sweat. Wet hair, wet bed clothes....
It's not wee as he wears pyjama pants and when he does wee the bed, it smells of wee obviously!
He sleeps under a duvet and it's not even very warm tonight. When it is warm, he sleeps under a thin fleece blanket.
Does anyone else's child do this/have this issue? He's fast asleep but I'm concerned why he's so sweaty.

Ds 5 is like this and always has been.
Dh is like this also...
Ds just goes to bed in his pants and a sheet which seem to help.

My son is 6 and is the same, absolutely soaked through when I check him at my bedtime. His pillow case has white salt deposits on it from the sweat drying out! Don't think it's abnormal, just make sure he drinks enough in the daytime to replace fluids