HI Im used to wear boxer shorts for my undergarment and i wanna change for briefs is there any halachic problem with it?
I can’t say that it is a halachic problem, however there is a preference to wearing boxer shorts or boxer briefs, because it isn’t snug against you, as snug briefs can cause warmth and stimulation. See https://dinonline.org/2017/06/27/mens-undergarments/
Nidda 13b regarding the michnasayim of the kohanim that was made in a way that that area should not be snug. Additionally, see O:CH 74-5, and M:B 74-20, Piskei Teshuvos 74-9, Orach Ne’eman 74-13.