BIG-IP AFM DoS Device Protection source IPs logged?

Logging on a DoS firewall needs to be carefully dialed in. If we were to turn on source logging by default, a 3DoS could fill a BIG-IP disk in minutes, or even seconds, depending on the attack. Unfortunately, the answer to your question is 'No,' however.. I would highly encourage you to get a dedicated physical link on your F5 - as big as you can get it.. maybe 2 ports per box, aggregated - for logging, if you want to do DoS logging.   Then, you need to set up a logging profile:
https://support.f5.com/csp/article/K51266926

That should be enough to point you in the right direction.