Naturally his clothing and how he wears it represents his confidence in emulating Vader!
In the Force Awakens he only has his hood over his head when feeling confident. After Hux’s insinuation that the Supreme Leader would be furious if the Droid escaped Kylo Ren is seen sulking in front of a computer with his hood down and has a tantrum when informed that Finn aided the Droid in escaping.
He later has his hood up after his officer informs him of the scavenger and seems confident since Hux is taking the responsibility for everything then Snoke insinuates that Kylo Ren might fail to kill Han Solo and in a scene after that Kylo Ren is seen without the Hood entirely as he feels utterly shamed that Snoke noticed him feel the call to the Light.
After the pep talk from Vader’s Helmet(actually Darth Sidious) he is seen with the hood back though down as he watches Starkiller Base blow up worlds. Then he is seen leading the troops to reclaim the Droid having put his hood up again as he has regained his confidence.
After capturing Rey he is seen having his hood down either because Hux lectured him or because he is insecure after reading Rey’s desire to kill him in her mind. It doesn’t take long for her to get him to remove the mask leaving him emotionally vulnerable.
After Snoke tells Kylo Ren to bring Rey to him he puts the mask back on yet keeps the hood down only to find her missing causing him to fly into another tantrum and is seen without the hood at all following that as he is feeling incredibly insecure at the moment to the point of easily being ordered by Han Solo to remove his mask.
In The Last Jedi he is seen wearing the Mask with a Darth Vader-like Cape because he thought that his killing of Han Solo at the least made him worthy enough for a long cape even if his defeat at Rey’s hands made him unworthy of a hood.
Snoke of course declares him unworthy of even a hoodless cape as well as the mask causing Kylo Ren to discard both until he kills Snoke upon which he regains confidence enough to reclaim the cape though not the mask as Rey still knocked him out during their Force Tug-o-War over Anakin’s Lightsaber!
In Rise of Skywalker Kylo Ren discovers the existence of Palpatine and adds a hood to his cape as if in anticipating that his killing of him would restore his confidence!
After Palpatine informs him that Rey is Palpatine’s Granddaughter explaining her constant victories over him he reforges his mask and wears it with the hood down.
After Rey causes his ship to crash in the desert he removes the mask but after she shows Force Lightning proving Palpatine’s explanation for her victories he regains confidence enough to wear the mask again.
I dare say if she hadn’t crashed his ship before her Force Tug-o-War he wouldn’t have removed his mask and her demonstration of Force Lightning would have resulted in him having his hood up in confidence!
He takes it off later to attempt to persuade Rey away from his ship’s ledge only for her to escape anyways leading him to put the mask back on only for Palpatine to threaten him with being attacked by the Final Order Fleet if he doesn’t kill Rey. He is not seen wearing the mask again after that.
If Palpatine hadn’t threatened him there he probably would have had enough confidence to wear the mask when facing Rey and the act of wearing the mask would make him confident enough to resist Leia’s attempt to call him to the Light ultimately resulting in Rey’s defeat(with capture resulting in him having his hood up)!
Kylo Ren’s discarding of his mask as well as his insecurities and ultimate return to the Light are all the result of Snoke and Sidious browbeating him constantly!