It is always a good idea to have a lawyer prepare your trademark application. Depending on the jurisdiction, you might also need their help with filing.
For example, in the EU, a legal representative is necessary for applicants outside of the EU/EEA. Otherwise, you may file your application on your own. The same applies to the US; only foreign-domiciled applicants are required to have an appointed US attorney. For the UK, there is no requirement for the application to be filed by a licensed attorney.
We recommend hiring an experienced lawyer or law firm to cover the whole trademark registration for you in case some issues arise during the process (such as Office actions issued by the IP office or oppositions raised by competition).