Time for Timer
My first instinct would be to have a 555 astable-configured at 10 seconds per pulse. Insert a momentary button switch on the power lead. Output starts positive then after 10 seconds pulses negative for a time period that you can adjust also. The only thing is: it will go back positive and pulse again after 10 seconds if you keep holding the button, and so on.
I like this better: If you want it to start negative and pulse positive, take its output (Pin 3) and go into Pin2 on another 555 chip that is monostable-configured. Its Pin3 output will pulse positive. (Or use one 556 to do both. Output Pin5 to input Pin8.)
Here's some good ol' Forrest Mims pages with schematics and time tables from the ol' Radio Shack books they used to publish...
I'd love to hear back how it goes AND what your application is for this.