When I sketch SW used to automatically create coincident relationships if the cursor was close to a entity on another sketch. It is now no longer doing that. I have Automatic Relations, Automatic Solve and Enable Snapping on. I have all options selected under System > Relation/Snaps.
Below is a screen shoot of sketching. The cursor does not show up but normally there would be an automatic coincident relation created by SW on the end of the tagent arc (blue arc) to the spline in another sketch (the gray spline).