In Telegram go into Settings, Privacy and Security, Groups
Here you can change who can add you to groups, change that from Everybody to My Contacts.
With regards to checking if an app is doing this, I personally doubt it's an app doing it. I reckon it's just ad groups who have your telegram name. If you did still think it was an app doing this you would need to manually deduce which app is doing so, by checking running apps and disabling apps till you figure out which app may be calling the Telegram API to launch a group. However I'd just recommend my top suggestion of preventing random people from adding you to groups.