Smells are hard to definitely attribute, especially transient ones. Try to mentally log under what situations you note the smell and a solution will eventually present itself (or the smell will go away).
Coolant, brakes, wires, fuel, oil and exhaust (six "biggies") all have unique smells, although sometimes brakes/wires and insulation all smell similar.
Burnt smells like wood or weeds are not typically found emanating from a car and are environmental (ditto for diesel smells).

Aren't these old cars fun? Drive 'em well.

Mike!