When I try to evade, Ryder cloaks. Is this a bug?
It started while I was doing missions on Havarl.
This is not a bug, it's a feature. Cloaking when evading is a perk of the upgraded Infiltrator profile, called Cloak Evades. As you put in more skill points in Combat and Tech, you will upgrade your profile and gain an extra passive perk.
If you don't like it, the only way to get rid of it is to use a different profile.