Macbook Air 2019 misbehaving. Fan loud + not charging - normal battery health…

My 2019 Macbook air has started misbehaving and rapidly detriorated in the past 5 days. Started with the fan blowing extra loud despite only doing normal activities. Restarted it several times and it continued to fan loudly. Have checked CPU and nothing major happening.

Two days after this started, the battery began to drain quicker than usual, and will not charge properly. Keeps charging then disconnecting in rapid succession.

Today I left it at 80% having closed all apps, with lid closed and plugged in. Came back 2 hours later and fan was still on full power and battery had drained to 5%!

System report says battery health is normal and still has low cycle count.

What else would anyone suggest?