Weightlifting splits

I will try and provide as complete and nuanced an answer as possible

Firstly, for your main question about whether you are resting the major muscle groups too much: In general yes, frequency is more beneficial when it comes to targeting muscle groups BUT that return also diminishes with various factors like training experience, recovery ability, programming. Someone who has been lifting seriously for at least 6 months to year might see the benefit of frequency dissipate and moving to something that gives each muscle group more rest is usually the path forward.

That alone does not mean you should switch to a full body right away. Some things to consider before moving to a compound movement focused strength program: injury history, medical history and restrictions, mobility and history in sports.

The best advice I can give is that if you live in the US, you might see if you can get a hold of a Starting Strength certified coach. They list their coaches here In lieu of that option, they also offer online coaching. Another good resource would be Dr's Baraki and Feigenbaum at Barbell Medicine who are medical doctors, powerlifters and Starting Strength certified coaches. Between those two resources and their blog articles, I think you will be more comfortable making a decision whether to get coaching or do it your own.

Which brings me to going it your own way: If you choose to start, I would highly (HIGHLY) recommend reading the book 'Starting Strength' by Mark Rippetoe. (The numerous mentions are not that this is the program you should choose but that it is generally a good starting point. )

If you do start on your own and if you choose not to go the coaching route then the next step would be to watch a ton of videos to understand proper form for all the lifts. Practice the form with light weights, maybe get a gym staff/personal trainer to check and the last step might be to video yourself and get form check advice here or at another forum of your choice.

Gains can come quick and fast once you nail the form down. But if the form is off, an injury especially at an older age can derail you quite a bit. Keep us updated and Good luck! Congrats on the weight loss