I always play terrible at the start of online sessions and I don't know how to prevent it :|.
It's a question of nerves. Once they have settled I can play for hours and hours and not make any significant mistakes, but until that point I have to negotiate a minefield of uncertainty.
I have tried the obvious things, like dropping down stakes, playing fewer tables, and analysing past sessions before I play. It helps a little but not as much as I'd hoped.
I'm currently playing relatively low stakes - 100nl when I have played as high as 1knl in the past. I would still be playing that high today but these moments before I can get settled are too big a leak!
Any advice would be greatly appreciated