Week and a half before my trail half marathon and am doing good overall but have this kind of problem. It takes about 2 miles now for my lower legs to feel right. They feel kind of tight and tired. Then after a couple miles I have no problem. Has happened on my last 2 runs and don't know what to make of it. Not sure if I need more miles or to ease off. Probably will opt for more miles!
I have a number (could be 1... That's a number!!!) of trail races scheduled for early 2012 and need to make sure I can handle more mileage. So I have already made the commitment, I'm training and now I just need to succeed! inmotionfit.com !

Trails are most likely the only running I will be doing for quite some time. Much more interesting to me. Less the monotony of just pounding the same pavement. Have one half marathon pavement race I am doing in early December but after that no pavement at all! Trail running has a way of a feeling of the miles going by faster... Even though your pace will ALWAYS be slower! Hard to explain how that happens but it seems that way to me. More of an accomplishment type deal just to finish and can't worry about avg. pace.
Oh well, can only do what I can do!... Doing the best I can with what I got!