>1. Anyone else deal with this?
Oh yeah.
>2. If you do what do you do about it?
I'll answer 2 and 3 together. I loose motivation because I am sick of riding. I ride too much or the same route too much. I tire myself out. I take some time of the bike, don't even look at it, about a week or 10 days. This period I will do all my outdoor household things that I save up for this purpose. I.e. built a new planter box for my wife, rake all the rock of the land for planting grass (just built a new house), caulk around the windows, clean the window glass, paint the fence, plant trees, etc. In the evenings after a good day of hard work (but taking my time) I sit and read or watch a movie, have 2 HUGE cups of coffee and something sweet that I like.
OR
I go on vacation. One year we went white water rafting, another we went to visit the parents for a week, another time we went to BC
>3. What has been the reasons for your lack of motivation, what ever the reason for it?
See 2 above
>4. What should I do about my lack of motivation?
If it was a case of riding too much, or the same route too much I'd say but the bike away and do other stuff. In your case maybe 500 miles is already too much and you need time away. Try it see what happens. I always come back refreshed. By the tiem fall shows I am ready to swich over to my MTB bike and do some short 20k rides in the evenings when they get shorter and shorter.
Digger