Motion detector switch affected by heater?
Absolutely!  Most motion sensors are IR (infrared) detectors and they can "see" heated air as it moves.  If it moves fast enough it may trick the sensor into thinking that it's a human vs. just heated air.  In your case the heater may be hitting the sensor directly with its IR output.

Try redirecting your sensor so that it doesn't pick up heated air output from the heater and can't "see" into the output of the heater.

It may take some experimentation with aiming to find a good spot between ignoring the heater and detecting you.