NannySharonof3, as others have said, having a health check is a good idea, to see if there’s a particular reason for the lethargy. Then I’d recommend trying to get out in the fresh air for at least a small part of every day, and looking on YouTube at all the free exercise videos to find some exercise that would suit you and you’d enjoy doing. Starting your day with 30, or even 15, minutes of movement can lift your mood and get you in the right frame of mind to look after your health.
For me it’s Fabulous50s, Walking with Rick, and Leslie Sansome’s walking videos, but there’s a huge variety out there, dancing, yoga, chair exercise, step… They all recommend checking with your doctor before you start.
He’s not for everyone, but I’m a big Michael Mosley fan, and his ten minute Just One Thing podcasts give lots of ideas for improving your health with minor changes. I’d recommend his 5:2 diet plan as well - again, it doesn’t suit everyone but it worked for me and many others.
Whatever you choose to do, make sure it’s something you enjoy!