Multi-tasking gesture or double button push restarts device. Plus bonus problem!

Neat! So this is one of the few times that comes to mind where my iPad is doing something uncool and I've no idea how to fix it. Actually, as I type that, I'm reminded of something else and I'll jump to that in a moment.

First off, I've no idea how or why this started, but suddenly when I try to go to the multi-tasking bar either by doing a five-finger swipe up, or double tapping my home button, it is restarting the device (or maybe just the springboard, if it makes a difference).

When I do either of these things, instead of the frame lifting and revealing the "previously run apps and other stuff bar" it just cuts to a black screen with the white wheel, and then brings me to my lock screen to unlock the device.

I have an iPad 2 that is not jailbroken. All I know to try so far is to just turn off the device and turn it back on. That… didn't work. Has anyone heard of this happening before, or have any ideas short of doing a really bothersome restore?

*** Now to the other problem that I was reminded of in writing the first two sentences. I doubt this is related and is just something weird about my iTunes account.
My iTunes account seems to be backed up with past purchases/downloads and I've no idea what the issue is. For the past week or so, any time I've started to download a new app, it gives me a message "Unable to Purchase. 'Google' [an app that I've downloaded successfully and sits on my device] and 25 other items could not be purchased at this time. Please try again later."
I press "OK" on this, and then my new app downloads just fine. But I get a couple of apps that did tell me recently "Item is currently being modified. Please try downloading again later" when I initially tried to download them but later downloaded fine suddenly appearing on my springboard as attempting to download again and saying "Waiting…" only to adjust themselves soon later back to their fully downloaded appearance.

So, after writing all of that out, I'm thinking… Apple Store Genius appointment time? I thought it might be more fruitful and productive to post it here first where plenty of other smart people can give a hint or two. Thank you for any feedback.

 

Thank you for your help! I did the soft reset, nothing changed. I synced my iPad, then did a soft reset, and now my multi-tasking is back! So… something in between must have fixed that. So thank you!

I'm still getting that iTunes message though, and it appears to but doesn't actually try to download two previously downloaded apps (that I've now deleted from my iPad) only with their icons to disappear when I re-open and then close the app store.
So I think something's congested about my iTunes account, and I may just ask the Apple people about that sometime soon.

Many thanks for your help. I'm glad to know about soft-resetting now.