If you stop while biking up a hill, it is very hard to start pedaling again. Until you have developed 'bent legs', it is much too hard. That is why I always stop after cresting the top of a hill. It makes starting up again much easier.
Of course, if you get tired on a long uphill climb, this might not be possible. In that case, you should just try to find a level spot where you can start your bike rolling from a complete stop.
If you try to start pedaling uphill after it gets dark, it is even harder. Very hard to keep your balance. Of course, this depends on the geometry of your bike. If your crank is higher than your seat, it makes it more difficult to start up from a rest, particular uphill. If your crank is lower than your seat, I imagine it would be easier to start up from a stop.
I suggest that you limit the length of the uphill roads on which you pedal your bicycle, and that you limit the steepness of the hills you climb on your bicycle, until you have develop your 'bent legs' to the point where you can pedal uphill in low gear without zig-zagging too much from side-to-side. This will take time, and progressively harder effort.
Last edited by LWB_guy; 02-28-11 at 03:08 PM.