FormMaker Question Bank  allows you to create new forms in seconds (including self marking quizzes) using questions from a question bank you maintain in a Google Sheet. As well as using it to create new forms, you can use it to store questions from any existing forms you have edit access to. 
Form Maker for Forms is part of the Form Maker set of Add-ons it can be used independently or in conjunction with Form Maker and Form Maker for docs which can be used to save questions to your question bank from Docs and Spreadsheets quickly and easily.

The add-on allows you to select specific questions from your question bank or to select a specified number at random from the whole database or from sections of it.

This add-on is a fantastic Form Builder, Quiz Creator, Survey Maker, Form Creator, Quiz Maker,  Survey Creator, Form Importer, Quiz Builder, Form Maker, Survey Builder

Basic features are Free to use with limits on numbers of forms per month and numbers of questions per form. 
Premium features with unlimited quota is available for professional users from $2.50 a month. ($30/year)

You can purchase a licence to cover everyone in a commercial domain for $200. For an education/non-profit domain the cost is $75.

Form Maker Question Bank is one of a set of Form Maker add-ons. Form Maker (used in sheets) and Fom&Quiz Maker (used with docs) the cost is the same for each. If you purchase all three together you get a 50% discount so the price for a single user for all 3 add-ons would be $45