Quick warmup before descent
I'm 40, and have back and joint issues that make getting up in the morning hard work.  If I get-up-and-go its terrible for the first half-hour.  So here's what helps me:


Full flexion of joints.  That means pushing your limbs to the ir comfortable maximum extensions then holding for a few seconds, then a little further.  Nothing rough.
A hot shower - where possible.
Warmth - standing in a sunny spot helps a heap, as does pressing a hot coffee cup against sore muscles.
Food - eat your damn breakfast!  
Water - hydrate!
Warmup ride - Do a short loop or gentle out and back to get limbered up.  Not going hard, just getting fluid into your joints and heating the muscles.
Clothing - consider wearing a tighter compression top and pants.  These will get your muscles up to working temperature sooner.
Sleeping clothes - don't wear the riding clothes while sleeping - you want to relax not be constrained. 
Gloves - I wear some home-made cotton gloves that cover 2/3 of the forearm. Again these help with keeping warmth in.


Getting sufficient sleep helps immensely.  Whatever helps you get to sleep is good too.  A plain sleeping bag is better on a sleeping mat, and picking somewhere without rocks/sticks is best.  I've never tried a camping hammock but some people swear by them.