Heat blows "smoke" from vents

Is it coming from your exhaust. Does it smell like antifreeze? antifreeze has a sweet smell. That could mean a bad head gasket. Since it goes away after 15km, I'm assuming the heat expansion on the engine does away with the leak. It could also mean a lot of other things. Has your engine overheated recently?

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heater core or one of the hose did you check antifreeze level there could be a leak

The speed control of your fan has resisters that are in the venting system to blow air on them to keep them cool. If they overheat and or burn you will lose your low and medium speeds of the fan. If you run the fan at full see if the smell goes away. Your engine could be burning oil on the outside of the engine block, make sure that the weatherstrip where your hood meets the fresh air intake grill is sealing tight.

sound like AC COMPRESSOR clutch bearing going bad causing locking up putting drag on drive causing drive belt slip giving a burn rubber smell.

mine does the same thing.. it is a sign that you are burning oil kiddo..either that or antifreeze is finding its way into the engine through a crack or bad gasket.. check for oil smell and moist soot at the tailpipe, or a sweet smell if antifreeze..now if its a steam like smoke..thats normal byproduct of the burning fuel and goes away once the exhaust pipes and muffler heat up enough to blow out all the condensate water...

sharp acidic smell would be electrical
sweet smell would be coolant.

The smoke you could be seeing may be steam, your heater inside the vehicle may have a leak and causing steam to rise out of the vents, if you are smelling the steam this is what I suspect.
Engine vibration could be a number of things, check the engine mounts to start, one of them is probably broken.

Do you leave your climate control in the Auto position. This is bad. What happens is the evaporator which is located in the vents never dries out and you begin to grow mold. Does it smell musty, locker room type smell.
Also since it came out the heat vent it could also be a leaking heater core. Check you coolant level and reservior. If low this is an indication heater core is leaking. It may not of leaked enough to tell but usually these are the only reason the vents would smell unless a rodent ended up there and died.

if it smells like sweet antifreeze, it is
the heater core is not he A/C evaporator core.

the core fails due to not replacing the antifreeze coolant before it goes acidic ... (not doing service here)

are you getting leakage under the dash near heater box, blower area?

Heater core or one of the hoses are leaking. Low on antifreeze now so no heat.