Back when I was still using Ubuntu MATE about half a year ago or so, I started having this really odd problem where signing into my account after a reboot would bring me to a blank screen with only my desktop background and nothing else. No taskbar, no panels, not even the cursor if I recall correctly.
Some furious Googling brought me to a serverfault thread that suggested that switching to tty7 with CTRL + ALT + F7 followed by ALT + F1 to switch back would alleviate it... and it did! But the problem returned on every login.
So for about six months I just had that as part of my routine on any reboot. Log it, switch to tty7, switch back to tty1. It was stupid and I hated it. Mostly because I didn't understand what I was doing or why it fixed anything.
On a tangent, this is precisely the thing that makes people intimidated by Linux, I think... it's not so much the inability to do things. Rather, even when you are given a way on a silver platter, you don't feel like you're really in control because you don't know what the black magic incantation really does. It's a truly horrible feeling.
I never did resolve the problem. I eventually nuked that OS and paved over its ashes with Debian Testing + KDE Plasma 5, and I haven't looked back.