Welcome JoyfulGirl!
You definitely haven't lost your mind - you've just joined the rest of us here who really like riding our bikes. Clearly your bike has decided she wants to be moving, and she wants you to be moving with her!
As far as your goal of riding a century goes - that's a fine goal, but make sure to work up to the distance (as opposed to trying to ride a century right now). It sounds like you're on your way...
--- Denise