How to set up a systemd service to retry 5 times on a cycle of 30 seconds

To allow a maximum of 5 retries separated by 30 seconds use the following options in the relevant systemd service file.

[Unit]
StartLimitInterval=200
StartLimitBurst=5

[Service]
Restart=always
RestartSec=30

This worked for a service that runs a script using Type=idle. Note that StartLimitInterval must be greater than RestartSec * StartLimitBurst otherwise the service will be restarted indefinitely. The service is considered failed when restarted StartLimitBurst times within StartLimitInterval.

See https://www.freedesktop.org/software/systemd/man/systemd.unit.html#StartLimitIntervalSec=interval and https://www.freedesktop.org/software/systemd/man/systemd.service.html#RestartSec=