Since you haven’t confirmed you have an automatic transmission, instead of a CVT which isn’t indicated available in US and not knowing if available in some other country, I’m going to assume an automatic and offer some further info.
I had time today to look thru factory manual for automatic transmission, which didn’t offer any info concerning the P0730 code but it did answer one particular fact I was looking for. It does have a limp mode (fail safe) condition that allows driver to get home or to a repair center. It didn’t indicate what gear that was, but sounds like it might be 4th from what you’ve indicated by it hanging in that gear. Manual also didn’t indicate what to check if it enters limp mode, but a general search of that code which is failure to shift into correct gear offered suggestions.
First that communally popped up was to change transmission fluid and transmission filter. That seems the most likely first step in your situation, as trash in the fluid could at times cause spool valves in valve body to stick and not allow gear shifts and causing TCM to enter limp mode throwing the P0730 code.
Just to be clear it could still be a problem with TCM or sensors sending information to it causing this situation. The fact that turning car off and back on corrects it makes me suspect some electrical problem instead of fluid. But if you’re over 100,000 miles without fluid ever being changed there’s a possibility that is what’s causing it and is the least expensive first step, without the filter change which will run cost up because of labor required to get to it.