Most first MCU tutorials involve flashing an LED, can be done literally in minutes. That's where I started, and I hadn't programmed anything in a good 10 years. I chose AVR, as the instruction set was most similar to the 6502, which I work with before. An ATtiny13V costs $1.16 (about a month ago).
You could also use a 555 timer and 4017 counter. There are at least 2 other threads here that cover the circuit details well. Not sure what the title was, some searching should turn them up for you.
Finally, if you put this on your car or bike, the police won't like it, and at the very least take it away, maybe you too. Bummer if your name is Rodney King...