If you feel burned out about one aspect of Magic but feel like it's still an important part of your day and you want to keep playing, focus on something else. If no part of Magic seems to make you excited, yeah, you're probably burned out.

I'm in a bit of a different situation than you are, it seems, but I switch between formats frequently to keep myself from getting to where you seem to be right now. Tired of re-building a deck every other week? Switch from standard to modern. Modern meta gets too samey while a ban needs to happen? Play legacy. Need to eat and make mortgage payments but you're tired of playing your current legacy deck? Pauper. Want to test your deck-building skills while listening to people who have no idea what they're talking about make frustratingly bad card evaluations? Limited.

Maybe I just need a break. I still like staying current with the MTG news and spoilers but the urge to play isn't there right now.

Sounds like it, yeah. You sound pretty bummed about it, but you can always come back.

This brings me to my next point...should I sell my standard staples or just hope that feeling of wanting to play comes back soon?

You're the only one who can answer this, but from reading the rest of your post, if you could use the cash, probably the former.