Pulse is the function of your hemodynamic system. This is governed by many things. your B.P. blood volume, your mental status anxiety, heart function, nervous system specially autonomous nervous system. As you have mentioned that your pulse rate increases on standing, it is most likely due to pooling of blood in lower limbs which stimulates heart to pump more blood by increasing the rate for safety from collapse as blood is not reaching to brain in adequate amount. You are advised to sit from lying position for some time for the system to stabilse and then slowly stand carefully with support. You may also consult Cardiologist for further advise and investigations.