It is not necessary to form an LLC or any other business entity before you register your trademark. Either an individual or a company can be the registered owner of a trademark.
If you operate your business as an LLC or other entity, it's advisable to register the trademark in the name of the company rather than an individual. This can help to protect the trademark if the ownership of the company changes or if individual owners leave the company. It can also make it easier to transfer ownership of the trademark if necessary.