Your campaign may be more likely to have performance fluctuations when its budget is limited. This is because Google Ads works to ensure that your campaigns don't exceed their daily and monthly spending limits, which can cause decreases in spend and serving when close to these limits.
What you can do
If your campaign’s status indicates that it's limited by budget, check the budget report to better understand your campaign’s spending relative to its average daily budget and how this has impacted your performance and spend limits.
Consider increasing your budget to make sure that your campaign has enough budget to be able to serve throughout the day.
Need something else?
Check other common reasons why your campaign performance is fluctuating.