Hall lighting on then goes out!!!! Mystery

I have a long hall and have two light fixtures in the ceiling, had them on and I noticed that one was OUT at one end of the hall, checked it and started to take the glass down and it came back on, I put a new bulb in it anyway and put the glass back on over the bulb and turned the light switch on and one came on the one I put the bulb in did not I even tried tapping the outside of the glass nothing...This has never happen..So please handy people out there give me a hand as what to do next please. Does it have a short you think??? I don't know why it would short while it was on then come back on while I was taking the glass off and then back on by touching the thing the bulb goes into..Help Please, Thanks, Shirley
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