Some services you might disable are:
1. ModemManager.service (unless you use a dial-up connection).
2. If you don't print files over the network, you can disable cups.service and cups-browsed.service.
3. If you don't use snaps, you can disable that one as well as related services. snapd.service, snapd.apparmor.service.
You can disable those by launching the terminal and running:
sudo systemctl stop name.service
then
sudo systemctl disable name.service
The first command stops the service if it's running, and the second one disables it from running at boot. Also, if possible, try upgrading storage to a SSD, this will improve startup time and responsiveness for apps hugely.
Hope this helps!
