It is typically used in DA reactions to inhibit polymerization

Please, do you have any paper talking about this point?

Many thanks

http://www.eastman.com/Online_Publications/WA80/wa8003.htm

http://orgsyn.org/demo.aspx?prep=CV6P0454

A small amount of Hydroquinone is added to the reaction mixture “to inhibit the polymerisation of the participating dienes/ dienophile of the substrate in Intramolecular Diels-Alder Reaction”. Thus Hydroquinone acts as polymerization inhibitor.