I'm not entirely sure that I'm using the right term, but I think you'll get the picture.
Last time I was out riding on my old ten speed (BRC, mid 80s?) there were a few times when I was pedaling and the freewheel was not catching. Pedal forward, backward, same feel. The first few times I thought the chain had popped off, but then I stopped and was able to recreate the situation pedaling by hand. The cogs were spinning forward, rather than catching and propelling the wheel. I found that by pedalling steadily it wouldn't slip, then the problem faded away. The next 50 miles were troublefree, except for sore legs.
Is this a common problem (not the legs)? Can this slipping freewheel be fixed, or does it need to be replaced? The bike is kind of a junker but fun to ride. Thanks!