If it's only been a week I guess there may well be other possibilities but it might be worth having a read up on POTS (postural orthostatic tachycardia syndrome) if it goes on longer and you're having other symptoms too?
https://en.wikipedia.org/wiki/Postural_orthostatic_tachycardia_syndrome
Mine can do that when I have stomach issues an overly full stomach or if I am slightly dehydrated. Is this new for you? The rate isn't terrible high but if this is new then just go and see a doctor and get a check up to make sure there isn't an underlying issue contributing to the rate.