Incomplete Astable 555 Circuit Triggering
From your oscilloscope, the frequency of the output seems to be around 50Hz (or could be 60Hz if you're in the US or other countries - it's not that easy to see the exact period). When you put your hand near to the white wire, you could be coupling mains electromagnetic radiation into the circuit. The 555 timer can be used as a schmitt trigger in certain conditions - generally with the trigger (pin 2) and threshold (pin 6) pins together.

If the threshold pin isn't actually connected to anything, it might be capacitively coupling to the trigger pin.

In a sentence, your body acts as an antenna for mains, bringing your body near to a circuit with floating inputs will couple some noise into the circuit, potentially producing an effect like this.