A few months back, I had a 'turbo-flat' as a 2-inch nail found its way to the rear tire. I feared there may be damage to the tire, but after checking it out (and having the bike mechanic take a look, there did not appear to be any problem.) After that, the bike seemed to run fine for the next few months.
Three times in the past month I've gone to the garage to get on my bike in the morning, and found the rear tire (700x38) flat. In each case, I had ridden the previous night without any problems. and after each time, I checked the tire and wheel for noticable puncture points, and didn't find any. The second time, I just pumped up the tire road a mile, three hours later pumped it up again, and road a mile back home. Then I replaced the tube, and found there was a small leak roughly opposite the valve. So, it appears that the pressure may have been a little low, thus causing the valve to puncture the other side of the tube - though the puncture was small enough to allow riding on it for the short time.
After that, I put a 'slime filled' tube in place. In theory that would help 'patch' the quick leak if it happened again. However, this morning, the tire was again flat. I pumped it up, and spun it around a bit, and then rode in to work. It seems to be at about the same pressure three hours later. So that leaves a mystery. If the tire seemed to run fine last night, and spinning it around seemed to allow it to maintain the air, how did it end up flat this morning?