User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:95.0) Gecko/20100101 Firefox/95.0

Steps to reproduce:

1. Open Firefox 95.0 in Linux (Xubuntu Xfce Uma in my case)
2. Do some random surfing, so that the cache fills up.
3. Close Firefox and immediately start it again.

Actual results:

Firefox starts with a transparent content window.
It seems like the cache clearing somewhat delayed the exit process and cause it
Closing Firefox, waiting for a few seconds and starting it again solves the issue.
This was introduced in 95.0, no problems in previous versions.

My machine is also quite fast (6 core Ryzen).
The required wait period increases the slower the machine is (tests on a 10 year old Celeron revealed a 5-6 second wait period).

Expected results:

Firefox should start right up in useable condition.

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

I was able to narrow down the cause for the problem: it seems to be related to the i915 graphic drivers.
I have a laptop, which is on i915 by default but can also has a dedicated nVidia chip.
Once I switch to nvidia via the Optimus tool the problem is gone and back when I switch back to i915.