I agree with everyone saying get an electrician over to sort it out for you. But in the meantime you could try a line conditioner like this to allow you to work around the issue:
https://tripplite.com/1800w-120v-power-conditioner-automatic-voltage-regulation-avr-ac-surge-protection-6-outlets~LC1800
(get the right wattage size for your needs there are multiple models)
I use one myself and while I don't have any issues I do hear the relays in the line conditioner click on and off every time my AC starts and the LC "boosts" the power.
https://tripplite.com/1800w-120v-power-conditioner-automatic-voltage-regulation-avr-ac-surge-protection-6-outlets~LC1800
(get the right wattage size for your needs there are multiple models)
I use one myself and while I don't have any issues I do hear the relays in the line conditioner click on and off every time my AC starts and the LC "boosts" the power.