The very fact that your baby is well in between fever spikes proves that this is more likely to be a viral infection.
Don't panic and start antibiotics now. Just hold fire.
Wait for 2 more days. If fever spikes are getting more frequent and high fever is noted, go for blood counts and blood cultures. A urine routine should be done as well. If anyone in the family is having headache, cough cold symptoms or fever, get a covid 19 RT PCR done.
Hope this helps!
Next Steps
blood counts, urine routine
Health Tips
Use Babygesic or paracetamol drops as required, not exceeding the maxm daily dose.