Idle drops low then stabilizes

[alk01]

This only happens on a cold start in any temperature to my 1985 325e BMW. While parked & running for about 2-4 minutes, idle drops low for about 2 minutes then stabilizes. When the idle drops while driving, car will not accelerate when pressing gas pedal. I am forced to tease the pedal (press & release constantly like tapping) to get it to move forward with major hesitance. Once it stabilizes, problem resolved. Please advise, thx!