There are two cluster-wide blocks and they are documented here. Neither of them is automatically applied. There are also a number of index blocks (search for blocks on that page) only one of which (read_only_allow_delete) is managed by Elasticsearch based on disk usage. Elasticsearch does not add any blocks based on heap usage.
Other blocks may be applied as a consequence of your actions or configuration (e.g. freezing an index makes it readonly, as do some ILM actions).