Bubbling from Toliet

For context - I have a one story home, 2 bathrooms. We have a septic tank and I got it cleaned when we bought the house in October of 2025.

Issue - I've noticed when we shower the toilets bubble and don't flush but everything is fine when the shower isn't running. This doesn't happen when we use the sinks or anything else that I've noticed.

I saw a post recently that had a similar issue and most people said main line clog or partial clog, etc. I just wanted to make sure that's what this is before I hire a plumber. The other post I believe was on city sewer so I'm questioning if it's the same issue or if this is something normal from septics. Any information or insight helps, thank you!