I'm pretty sure it's due to radio interference.
When passing near a BTS (Base Telephone Station) particularly powerful (in the countryside usually...) it happened couple of times to me.
No harm though...
Unfortunately we are flooded with radio signals of all possible frequencies: from 50Hz (60Hz in the US) up to microwaves.
The whole spectrum is full!
There's plenty of cars not cranking up or gates that suddendly open etc.
It's a wireless world!
Now we know that Jay does like Silver!