Question: [Friday 18th Tamuz 5780]
May one sleep in his clothing or should he wear pajamas according to Halacha?
There is no Halachic obligation for one to wear pajamas at night, and hence he can choose to sleep with his clothing, even though this is not the normal way of the world [seemingly due to reasons of comfort]. Nonetheless, it is proper for one who slept in his clothing to change clothing upon awakening prior to saying the morning blessings in order so he can say the blessing of Malbish Arumim according to all opinions. [However, there is no problem to Daven in these clothing so long as they are kept clean.] Likewise, it is recorded in Sefarim that one should not sleep with his shoes on, and nor should he sleep with metal attached to him, such as a belt.
Sources: See Yuma 78b regarding shoes, that one who sleeps in them tastes death, Chida in Avodas Hakodesh Tziporen Shamir 7:112 regarding metal and Piskeiy Teshuvos 239:14 regarding shoes and metal; Likkutei Maharich that sleeping with shoes it is Kasha for Shichicha; See here regarding malbish arumim https://shulchanaruchharav.com/halacha/must-one-receive-the-pleasure/