Why not try...?
My suggestion to you today is... pillows!
If you find your body feels achy when you wake you might benefit from trying some variety in your sleeping position. Unfortunately this is easier said than done. Despite the best intentions in the world, once asleep it's pretty hard to tell your body what position to lie in.
Chances are you have a favoured position. For many people this is a variation on a fetal position. This can be a very comfortable position and can make you feel very safe and secure - perfect for sleep you might say!
But... this position flexes so many muscles. In particular it flexes the area around your lower back and hips. If you sit for any significant amount of time during the say (if you have a desk job, for example) then you are already holding this area in a flexed position during the day, and if you then sleep in a fetal position at night - these muscles never get to relax!
It is unlikely that you will be able to easily stop your sleeping body to break a lifetime habit of sleeping in a particular position and I would say that if you are sleeping soundly for a good amount of time then that's great! Good sleep is the most important thing you can give to yourself and I wouldn't want to suggest anything that may interfere with this.
If you wake feeling sore and achy then you may want to consider using pillows to improve your natural sleeping position.
With the fetal position example, a small pillow or rolled blanket between the knees can open up the hips, giving them a more balanced feel and hopefully reducing any soreness in the morning.
If you lie on your front and find your neck and shoulders feel tight in the morning, experiment with rolled blankets or towels under your shoulders/upper arms to ease the strain on your upper trapezius and neck.
If you sleep on your back a pillow under the knees can help ease lower back twinges and ease the stretch on your psoas and hips.
Of course these are all starter suggestions. How you sleep is very personal and unique so my suggestion is really just to experiment with propping yourself into positions that ease your body. See what works for you and remember to change things around if you find they no longer work for you!