There is an abundance of documentation on
dhcpcd. It's available online for the cost of an Internet search, and available on your system in
man dhcpcd. It appears you've not done much research.
We can certainly understand that being unable to access your RPi will limit your troubleshooting options, but there are several methods available if your network is down. If you have occasional outages, you should look into these alternatives. Perhaps the easiest is to obtain a cable to connect a monitor to your RPi.
Also please understand that there are literally innumerable possible causes for the situation you've described in your question. We have some extremely knowledgeable people here, but unfortunately no mind readers or diviners. In other words, if you can't articulate your problem, your prospects for getting a useful answer decrease, and the prospects for having your question closed increase.
All of that said, here's a couple of thoughts that may help:
dhcpcd works well in most situations for most people. Its wide distribution is a testament to the fact that it's very robust. When it fails, it's often due to changes in
/etc/dhcpcd.conf made by a user. If you've not modified
/etc/dhcpcd.conf, consider restoring it to its default. A manual intervention is possible, but this is a bit of a kludge, and you can't access your Pi anyway:
sudo service dhcpcd restart
The internet search referenced earlier contains this old thread where the problem you describe is discussed, and solutions are proposed. If I understand the discussion, the issue may be caused by how the OS starts
dhcpcd. In RPi OS
buster the file
/etc/systemd/system/dhcpcd.service.d/wait.conf contains the startup code for
dhcpcd. I believe the default is the following line:
ExecStart=/usr/lib/dhcpcd5/dhcpcd -q -w. Perhaps someone more familiar with this can chime in? If not - try the solutions proposed, and let us know how that works.