Possible issue after thermostat change

[Bobtail_Bimmer]

Hey guys got a quick question. I have read through about 20 posts and not found an answer. I changed my thermostat on Saturday since my car was not blowing heat but warming up as it should. I bled the system, ran it and bled it again on Sunday and everything has been fine. Coolants at proper level, no leaks, etc.

Coming to work this morning I noticed that the temp needle was rising pretty fast but never went past middle. Stops about a millimeter to the left like it always has. Car was blowing heat but still not as good as it used to. I pulled in to a gas station and tried to bleed some more but no bubbles. I cut the heat off and waited and felt the lower hose and it was getting hot where the coolant was passing through so I know my new thermostat was opening and closeing as it should. I bought a failsafe just to be safe!

As I was leaving to go to lunch I didnt even make it out of the parking lot and the needle started to move. Went roughly less than a quater mile and it was almost at half way point. Came back to work and let my car run while a watched the needle. It never went past middle and stopped at its normal point. Tried beeding but this time was on level ground and got nothing but coolant. The top hose was hot! I shut the car off, ate my lunch and here i am.

I am wondering if it sounds like there are still possible air bubbles that I havnt bled yet or if it could be something else? Your help is much appreciated!!!