I wouldn't start HIIT unless you can (maybe you already can?) comfortably jog for an hour.
If you can't do that yet, work on that.
However, HIIT principles can be used in many ways. Why not try this next time you're working out? It's a Tabata Protocol 4 minute HIIT workout...
Warmup! (Very important step!)
For 20 seconds, do as many squat thrusts as you can. This is where you squat down, then as you stand up you also extend your arms above your head (if you have no blood pressure problems) and reach up. No weights - just body weight. Rapid movement is the aim, not perfect form.
For 10 seconds rest. Just wait.
Repeat x8. For four minutes. You will be hating the last two sets, and should be VERY exhausted after the entire thing.
Cool down with a 5 minute walk.
See how you feel the next day. Always wipes me out when I haven't done it in a while.
Deb, in New Zealand