Uuuugghhh…MOC-blocks are the worst, as a rather creative person…losing that kinda feels like being less of a person. I crave ideas and constantly executing them, so I’ll have to give some advice.
Look around for something that previously kickstarted your creative system: Maybe it was artwork, a piece of media, or another MOC. Something out there has helped you before, try to harness whatever has helped you in the past.
Search for inspiration in something else you enjoy: Pretty self explanatory here, I personally look into a ton of different Gundam designs or something whenever I need that creative pep, getting those gears and appreciation for good design going.
Revamp a old MOC or set" Once again, pretty self explanatory. Try to bring a old set or MOC up to your new standards while following the established ideas for the original verson.
Maybe you just need a break/breather: Sometimes you just need time, maybe you have strained your creative systems a bit too far. Perhaps something else is clouding your creative vision and needs to be resolved. Just take it slow, maybe your brain will piece something together in the downtime.
I spent a lot of last year with brutal growing pains as far as MOCing is concerned. One of the hardest things with MOCing is the fact you have to constantly one-up yourself, which left a lot of MOCs on the cutting room floor (or…bedroom floor in my case) last year.