Can I do SEO on my own?

Yes, to a point. Claiming your Google Business Profile, writing decent page titles, and fixing obvious technical issues are all things a business owner can do without help.

Where it gets hard to keep up is the ongoing part: ranking against competitors who are actively building content and links, keeping up with algorithm changes, and finding the time to do it consistently every month. That's usually where DIY SEO stalls out, not at the start, but a few months in.