Is this jump in HR lying the whole time normal?

Just measured my HR today to see what it's doing and saw this.

21:45ish HR on pulse oximeter laying down fluctuated between 73-101 within 3-5 minutes

BP monitor

21:53

137/90

HR 79

21:54

138/87

HR 80

Pulse oximeter

21:56

HR 70

22:02

HR 92-95

Just confused. Most of the time my HR goes up a lot when I stand/walk but I've been laying the whole time in these?? I've been relaxing and lying on my bed for the past few hours.