This is your problem right here. (Most likely) When you start the car, the ICE will kick in in about 10 seconds... and will continue to run until it reaches its normal operating temperature. (or somewhere near normal). This will take about 10 minutes if the outside temp. is in the 40s (F).

Since your drive to work is only about 4 miles, the ICE does not have a chance to fully 'warm up'- and if it does, it isn't at normal operating temp. for very long.

So you aren't actually getting any benefits from the hybrid because of your short drive time.

Try this: Drive your hybrid until the ICE is fully warmed up. (10+ minutes). Then drive your car around in town on flat roads at 25-35mph. (where there won't be much of a demand on the engine) If after another 10-15 minutes, your car still isn't operating in electric only mode... then you might want to take it to the dealer to be checked out.