Restarting postgres

No, there is no danger of restarting postgres using the init.d method.

However, to restart it because something weird happened is not a good idea, because it limits severely the amount of information you can collect to find the root cause and limits opportunities to fix it.

Also in all the years I have been involved with postgresql, I never encountered a situation in which a restart "fixed" the problem. The immediate 'incident' might be resolved but if there's a problem, it will still be there.

The only way relations would disappear on a restart of Postgres, would be if they were temp tables or created relations within an open transaction. When the db restarts it would close all connections and thus all temp tables would be dropped and open transactions would be rolled back. But anything that was committed would be safe from a restart.

Relations don't disappear because of a restart, you might loose some running transactions, but that's it. PostgreSQL does not destroy your database when it restarts, don't worry.