Random Interval Timers

Does anyone have suggestions for closing an electrical circuit at irregular intervals? It would be great for a vibrator if you never know when it will stop or start again. For that use case, the device needs to stay on for about five minutes and then off for two. You get the picture. I’m also thinking of someone here who uses airsoft guns for target practice. In that scenario, you’d want it on for 2 seconds and off for a minute (random timing would be ideal). Any input is much appreciated.