Blood pressures this high for short periods of time are probably safe but for prolonged periods of time it can be dangerous. High blood pressure can lead to strokes or heart failure.
I'm not able to explain why your blood pressure is doing this. Perhaps you are having releases of epinephrine for some reason. This would be associated with a rapid heart rate and feelings of anxiety (basically the fight or flight phenomenon).
I would recommend you follow up with your doctor about this to discuss the issue further and see if a cause can be found.
Advice and opinions given are based on the information provided and must not be considered an official medical recommendation. The limitations of the internet prevent an appropriate evaluation. Always consult your doctor if there is concern.