IF your mirrors are the same as mine (96 Roadtrek on 95 Dodge chassis), remove the cover screw on the bottom of mirror base and slide cover up to view the mounting base. You may have to turn the mirror inwards for this to slide up.
There are 4 #27 torx bolts that hold the swivel part of the mirror to the base. These may be loose so tighten them up. They also may be seized and have to be freed up to tighten. Sometime there has been some wear in the shaft and tightening still does not cure the problem. One person I talked to, removed the bolts and put some "removable lok-tite" on the shaft, reinstalled the bolts and adjusted his mirror before the lok-tite set up. Claims it solved his issue.
Mine worked by just retightening the torx screws.
Good luck