White smoke in engine bay

So my engine bay sometimes would start smoking white almost like its coming from the alternator..i know white smoke is usually coolant but it doesnt really smell like coolant it doesnt have that sweet smell its more of a rubbery burning smell..could it be the serpentine belt? The weird thing about it is it only starts smoking when i drive pretty hard then id turn the engine off for 5 min and the smoke will be gone..so its kinda on and off

White smoke in engine bay