This is a simple question that requires a nuanced answer. As a law firm, we always recommend use of counsel in the filing of a trademark. An attorney provides you guidance on the selection of a mark https://dunnington.com/trademark-talk-what-makes-a-trademark-strong/, and prior searches https://dunnington.com/trademark-talk-should-i-conduct-a-prior-trademark-search/.
But as a practical matter, no, you are not legally required to have counsel file a trademark application if you are domiciled in the United States. If you are a foreign domiciled trademark applicant or registrant, however, you must have a US-licensed attorney represent you.
The trademark registration process can take years, and may entail multiple substantive correspondences with an examining attorney from the USPTO. In the long run, hiring an attorney can save you money, as experienced counsel can help you navigate the clearance and registration process, and address post registration issues such as potential infringements and the maintenance of your mark.
