What you're describing sound like palpitations [link to NHS page]. As Olivia_H said, from the way you describe it, it's most likely caused by attacks of extreme anxiety. This kind of anxiety could be caused by sensory overload, or, vice versa, anxiety can make sensory overload more likely; but not necessarily.
So, the most important thing is probably to try and work out what is making you anxious; it could be something sensory, something emotional, or a bit of both. For some autistic people, who have difficulty with interpreting emotions (alexithymia), it's not always so easy to work out the causes of the anxiety, or it might be a delayed reaction to something that happened a while ago (I often have these problems myself.) If that's the case for you, try writing down the recent events in your life, and see if you can pick things out that you'd expect to be stressful; that might give you a starting point.
I'd definitely think about getting in touch with your doctor and considering counselling or going back on medication; especially if you can't find an obvious cause which you can fix to relieve the stress.
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