No. According to Section 52 of the CGST Act, 2017, TCS is required to be collected on the net value of taxable supplies made through it by other suppliers where the consideration is to be collected by the ECO. In this case, there are two transactions – where you purchase the goods from the vendors, and where you sell it through your website. For the first transaction, GST is leviable, and will need to be paid to your vendor, on which credit is available for you. The second transaction is a supply on your own account, and not by other suppliers and there is no requirement to collect tax at source. The transaction will attract GST at the prevailing rates.
(FAQ 25: E-COMMERCE)