The game can give you a few penalties for speeding in the pitlane most of the times.
Make sure you enter pitlane with your pitlimiter enabled not exceeding the maximum speed. However when you do the game can hand out:
Stop & Go; you need to come back into the pitlane within x amount of laps, to serve a penalty by stopping your car in the pit area of your team (red square). The game will hold you there for 10 or more seconds and releases you again.
Drive Through; if you receive a drive through penalty you should not stop at your box, but simply enter pitlane on the limiter and drive through the entire pitlane after you exit it again. This is a penalty for minor violations.
If you mix one of them up, your penalty will stay and you need to come back in again (happens to most of us ).