I would actually think that maybe something in you has just switched off the off button .
Remember you can go too overboard on doing something in your spare time and your brain might have switched you off (Hey at least its not a harmfull thing like drugs or alcohol though).
I would say take a break from the coin hunting , clear your mind for a while , then set a date to open your collection again in the near future , say six months away and see is the feelings return .
Dont worry if they dont just repeat the above task , and maybe think of selling up if you are really bored or fed up with collecting.
good luck!