Lindsay Lohan -- The Bizarre Sex Scene Demand

Lindsay Lohan was EXTREMELY hesitant to shoot a steamy sex scene for her new movie "The Canyons" last week -- but we're told, she quickly changed her mind ... after the crew fulfilled an extremely unusual request.

Sources connected with production tell TMZ, the scene required Lindsay to go topless -- but she was so uncomfortable with the idea of baring her bosom in front of the set's 10-man crew, she asked them to strip down with her ... to their boxers.

The crew was hesitant at first -- but according to sources, they eventually obliged, stripping down and shooting the entire scene in their skivvies ... and it all went off without a hitch.

You'd think Lindsay would be used to the idea of baring her lady bits -- she posed nude in one of the most widely-viewed Playboy issues of all time -- but who are we to judge?