Ok so there are a number of simple body weight exercises you can do from home with little or no equipment. Doing body weight movements along are probably not going to grow a large amount of muscle but the good news is, going body weight sessions at home will get you into the routine of training, will increase strength, help you burn a little fat, increase your conditioning and is a great way to get ready to join a gym and start weight training.
Try googling body weight exercises and you will find lots of helpful websites with pics and videos on how to do the exercises. Here is a small list of ones I like but there are lots more.
Push ups (lots of variations of push ups, feet elevated, hands narrow, hands wide)
Plank holds
Bodyweight squat or goblet squats
Rear elevated split squat (sometimes called Bulgarian split squat)
Walking lunges
Over head lunges
Chair dips
Pull ups (if you have a bar)
Inverted Rows (can be done under a table)
Burpees
There are lots of ways to set up a training session. Again heaps of workouts online, google is your friend. I have given an example below:
Pick 5 or 6 exercises.
Push ups - 3 sets, max reps
Bodyweight squats - 3 sets - 20 reps
Walking lunges - 3 sets 20 lunges (10 each leg)
Plank Holds - 3 sets 30 seconds
Chair dips - 3 sets, 10 reps
Burpees - 4 sets, 5 reps
I would complete 1 set of each exercise like a circuit and then repeat. So you start with push ups and do as many as you can, maybe 20 reps. You then catch your breath and move to body weight squats and do 20 squats, catch your breath, then move to walking lunges and do 20 (10 each leg), catch you breath ........ work your way through all the exercises. Then have a short break 2 mins to fully catch your breath. This is one set of each exercise. Now just do it all again 2 more times.
Do this session 3-4 days a week, days rest in between. Once you done this a few times It will get easier. You have lots of options to make it harder. You can add reps, so do 30 instead of 20. You can try to get faster, you can add another set, so do this 4 times instead of three. You can add resistance but adding weight. A back pack with a few backs of rice of flour will do the Trick.
I hope this helps a bit. Remember the most important thing now is to start something and set up those consistent good behaviours. Once the gyms open you will find it much easier to transition.
Good luck