Need some advice when starting a session

I have a problem in that when i first sit down to a session i always seem to lose initally.

i play $100NL 6-MAX and average +$30-100 per session whether that be one hour or 6, one table or 4. I can only play a few times/week so am happy with this. But what happens is I start and with 30-40 hands am ~$30 down. I tried looking at PT stats to see if there was anything but only that I am a little cautious. I generally play quite tight and then aggressive with something but rarely bluff.

Has anyone any ideas on how to improve this? I see others sit down, be aggressive from the off and create a table image quickly. The aggressiveness is something I am learning (I have only been playing 8months) and just feel a bit stuck...