Safari zooms on its own

Hello. Sometimes I open a webpage in a new tab in Safari and it opens in a "zoom in" mode, without me being able to restore it to original scale, even if I reload the page. The only option is to quit safari and re - open. No matter I use the trackpad or a mouse (not the Apple magic mouse), it happens. I am pretty sure I don't make any accidental moves. Does anyone have a similar issue?