Where to start looking for a reason when it is not clear where thousands of references to it come from?

Question

Search Engine Optimization

Yandex webmaster shows 11000 links to our site. We didn't buy anything. This year. At the beginning of the year there were 2500.
The site at 180 is not in the search. I suspect a competitor.
And also how to check if there are short visits to the site for a few seconds by any robots?
Prompt algorithm, please.

Answer 1

See what the links are through ahrefs or linkpad. Are they from different domains or from the same one? A couple of months ago, tens of thousands of links also appeared on my site, it turned out that one of the sites simply put a through link.