This is not the first time this has happened. Turns out the electric air pumps have a lower MBTF than anticipated. As mentioned, a reset should fix it (which the FA can easily do after getting approval from the pilots), but it is annoying. It's just like turning your computer off and back on again. That said, if the air bladder is actually broken (reset is unsuccessful), it gets fixed as quickly as it can get to wherever there are parts to fix it. As the OP did, a pillow or blanket to sit on makes it comfortable enough!

-J.