Unknown call when connecting to Bluetooth

[Android Central Question]

Since this past weekend, every time I start my car (also happens on 2 other cars so likely not car related), an unknown call is made which I then have to hang up on in order to get back into the infotainment system in the car. When this unknown call occurs, my phone does not show an active call and nothing appears in the phone's call log. I've tried deleting the Bluetooth cache, deleting and re-pairing the phone, rebooting the phone, and rebooting the car's infotainment system but it still keeps happening.

For reference, my phone is a Samsung S9 running the most up to date software version (G960WVLU4CSD2) from April 1/19. The car in question is a 2018 Honda Civic, and as noted the same issue occurs in a 2018 Honda CRV and a 2016 Mazda CX-3.

Thanks in advance for your assistance.