Left Turn Signal Flashing While Lever Not Engaged at Car Start

I recently just bought a 2012 Prius with 56k miles from my dad. He's had it since new and has pampered the car. I do have an issue with the left turn signal. It turns on automatically at the start of the car and won't turn off unless I engage the High Beam.

The turn signal lever is in the middle position, I push the start button, and the left turn signal starts flashing.
I turn the lever to signal right and both right and left turn signals flash (like the hazard). All the bulbs all still work, and this doesn't happen on a consistent basis, which might mean it's a loose wire. Anyone have any idea what this is?