Hello Jim,
Do use virtual machine (VM)?
How much memory is allocated on your machine?
What modules are provisioned?
Most probably you have high swap memory on your machine (you can check it via "top" command).
We saw such issue in case of not enough memory for signature update, so you can try to allocate more memory for you machine (if VM) or deprovision some modules.
In case of 8GB of memory we support only 3 modules at most.
Look at https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/releasenotes/product/relnote-bigip-ve-13-1-1.html#rn_supported_hardware for more details.
Thanks, Ivan