Self Service. To hyphenate or not?

Self-Service or Self Service.

For example, Self-Service restaurants, Self-Service Websites, etc..

Another example, multi-platform, multi-factor, etc..

Is the hyphen a must?

Solution 1:

As a compound adjective, yes, the hyphen is a must to avoid confusion in instances such as this admittedly rather contrived newspaper-type heading example:

Help your self service restaurants survive.

Is this:

Help your self! Service restaurants! Survive!
Help your self-service restaurants survive.
or
Help your self. Service restaurants survive.
?

Solution 2:

Hyphenate only as a compound modifier: I asked her to provide self service. It is a self-service gas station.