Do you sleep so deeply that you do not throw off the covers while asleep when you get too warm? Are you wrapping yourself up so tight that you just get too hot in the deep-sleep portion of the night? If so, drink some bedtime water. It will make you get up in the night to pee, and you can adjust the covers then while still mostly asleep for a lighter cover for the rest of your sleep.

Our bedroom gets way too warm toward dawn, when we close the bedroom door at peetime, to shut out the dawning light that would otherwise awaken us shortly-- but the heat builds up too much then, so we have had to adjust the timer on the thermostat to bring the heat up a little later in the morning.

As far as natural fibers for bedding-- you are using a mattress pad, right? If it's just sheet on mattress, that would cause a lot of heat buildup.

~Susan