Why does my toilet bubble every time I have a shower?

Hi dsellis and welcome, sounds like you have some blockage, you'll need to run a snake through the line, which means you'll have to take up the toilet and snake from there. Hang tight for a plumbing expert. Good luck

No plumbing expert but I think Partime is correct. Partial blockage, probably very close to toilet. Pull toilet and snake the line.