F5 Trunk port is connected to Cisco Switch Access Port

As Hamish said, the only time the F5 will send traffic across multiple links is when you tell it to.

For me that is most commonly performed using a trunk link on the f5 connected to a Cisco ether-channel at the switch (LACP). The other option that you can do to send traffic across multiple links and also multiple trunks is the VLAN Group.

In your case, if you have not configured a VLAN Group on any device then there should be no risk of looping. If your trunk/ether-channel configuration is setup correctly then that should function correctly also.

I always have a "private" connection between the HA pair of devices to use for things such as network failover and connection mirroring. This private link gets a VLAN assigned to it that is not present on the connection to the switch.

In short, as long as the same VLAN does not exist on the connection to the switch and the connection to the other F5 unit, you should not have issues. I recommend running two links to each f5 and switch as a trunk/ether-channel combination, and then run two links between the pair and set them up as a trunk, also. (We don't run access port configurations anymore, they are too limiting)